#define _CAT_SECURE_NO_WARNINGS
#include <stdio.h>
int main() {
    long long int n;
    scanf("%lld", &n);  //总牌数

    long long int str1[100] = { 0 }, str2[100] = { 0 }, str3[100] = { 0 }, str4[100] = { 0 },
                  str5[100] = { 0 };  // str1记录所有a；str2记录所有b；

    for (long long int i = 0; i < n; i++) {
        scanf("%lld", &str1[i]);
        scanf("%lld", &str2[i]);
    }  //输入每张牌的a，b点数

    for (long long int i = 0; i < n; i++) {
        for (long long int j = n - 1; j > i; j--) {
            if (str2[j] > str2[j - 1]) {
                long long int temp1 = str1[j];
                str1[j] = str1[j - 1];
                str1[j - 1] = temp1;

                long long int temp2 = str2[j];
                str2[j] = str2[j - 1];
                str2[j - 1] = temp2;
            }
        }
    }  //对cyy的牌从大到小进行排序

    for (long long int i = 0; i < n; i++) {
        long long int geshu = 0;
        long long int zhizhen;
        while (str2[i] == str2[i + 1]) {
            geshu = 2;
            zhizhen = i;
            for (long long int j = i + 1; j < n; j++) {
                if (str2[j] == str2[j + 1]) {
                    geshu++;
                } else
                    break;
            }

            if (geshu == 2) {
                if (str1[i] < str1[i + 1]) {
                    long long int temp1 = str1[i + 1];
                    str1[i + 1] = str1[i];
                    str1[i] = temp1;

                    long long int temp2 = str2[i + 1];
                    str2[i + 1] = str2[i];
                    str2[i] = temp2;
                }
            } else if (geshu > 2) {
                for (long long int i = zhizhen; i < (zhizhen + geshu); i++) {
                    for (long long int j = (zhizhen + geshu - 1); j > i; j--) {
                        if (str1[j] > str1[j - 1]) {
                            long long int temp1 = str1[j];
                            str1[j] = str1[j - 1];
                            str1[j - 1] = temp1;

                            long long int temp2 = str2[j];
                            str2[j] = str2[j - 1];
                            str2[j - 1] = temp2;
                        }
                    }
                }  //对整体的牌进行的内部的排序
            }
        }
        i = i + geshu;
    }

    for (long long int i = 0; i < n; i++) {
        str3[i] = i + 1;
    }  //用str3对数组二从大到小进行编号

    for (long long int i = 0; i < n; i++) {
        for (long long int j = n - 1; j > i; j--) {
            if (str1[j] > str1[j - 1]) {
                long long int temp1 = str1[j];
                str1[j] = str1[j - 1];
                str1[j - 1] = temp1;

                long long int temp2 = str2[j];
                str2[j] = str2[j - 1];
                str2[j - 1] = temp2;

                long long int temp3 = str3[j];
                str3[j] = str3[j - 1];
                str3[j - 1] = temp3;
            }
        }
    }  //对csf的牌从大到小进行排序,并联动数组1、2、3进行排序

    for (long long int i = 0; i < n; i++) {
        long long int geshu = 0;
        long long int zhizhen;
        while (str1[i] == str1[i + 1]) {
            geshu = 2;
            zhizhen = i;
            for (long long int j = i + 1; j < n; j++) {
                if (str1[j] == str1[j + 1]) {
                    geshu++;
                } else
                    break;
            }

            if (geshu == 2) {
                if (str2[i] < str2[i + 1]) {
                    long long int temp1 = str1[i + 1];
                    str1[i + 1] = str1[i];
                    str1[i] = temp1;

                    long long int temp2 = str2[i + 1];
                    str2[i + 1] = str2[i];
                    str2[i] = temp2;

                    long long int temp3 = str3[i + 1];
                    str3[i + 1] = str3[i];
                    str3[i] = temp3;
                }
            } else if (geshu > 2) {
                for (long long int i = zhizhen; i < (zhizhen + geshu); i++) {
                    for (long long int j = (zhizhen + geshu - 1); j > i; j--) {
                        if (str1[j] > str1[j - 1]) {
                            long long int temp1 = str1[j];
                            str1[j] = str1[j - 1];
                            str1[j - 1] = temp1;

                            long long int temp2 = str2[j];
                            str2[j] = str2[j - 1];
                            str2[j - 1] = temp2;

                            long long int temp3 = str3[j];
                            str3[j] = str3[j - 1];
                            str3[j - 1] = temp3;
                        }
                    }
                }  //对整体的牌进行的内部的排序
            }
        }
        i = i + geshu;
    }

    long long int zhizhen1 = 0;    //设置指针1
    long long int paishu = n / 2;  //记录cyy要取的总牌数
    long long int sum = 0;         //用以记录已经处理过的牌数
    long long int he = 0;          //设置cyy的和

    long long int k = 0;  //用以记录str5的个数

    while (sum <= n) {
        long long int max = str1[0];
        for (long long int i = 1; i <= n; i++) {
            if (str1[i] > max) {
                max = str1[i];
            }
        }  //用以找到str1中的最大点

        for (long long int i = 0; i < n; i++) {
            if (str1[i] == max) {
                str1[i] = str2[i] = 0;
                zhizhen1 = i;
                sum++;
                break;
            }
        }

        if (str3[zhizhen1] <= paishu)
            paishu++;

        long long int j = 0;  //用以记录str4的个数

        for (long long int i = zhizhen1; i < n; i++) {
            if (str2[i] != 0) {
                str4[j] = str3[i];
                j++;
                if (j >= 2)
                    break;
            }
        }  //取出str2中的两位

        long long int zhizhen6 = str4[0];
        long long int zhizhen8 = str4[1];

        if ((str3[zhizhen6] <= paishu && str3[zhizhen8] > paishu) ||
            (str3[zhizhen6] > paishu && str3[zhizhen8] <= paishu)) {
            if (str2[zhizhen6] > str2[zhizhen8]) {
                he = he + str2[zhizhen6];
                str1[zhizhen6] = str2[zhizhen6] = 0;
                sum++;
            } else if (str2[zhizhen6] < str2[zhizhen8]) {
                he = he + str2[zhizhen8];
                str1[zhizhen8] = str2[zhizhen8] = 0;
                sum++;
            } else if (str2[zhizhen6] == str2[zhizhen8]) {
                if (str1[zhizhen6] >= str1[zhizhen8]) {
                    he = he + str2[zhizhen6];
                    str1[zhizhen6] = str2[zhizhen6] = 0;
                    sum++;
                } else {
                    he = he + str2[zhizhen8];
                    str1[zhizhen8] = str2[zhizhen8] = 0;
                    sum++;
                }
            }
        } else if (str3[zhizhen6] <= paishu && str3[zhizhen8] <= paishu) {
            if (str2[zhizhen6] > str2[zhizhen8]) {
                he = he + str2[zhizhen6];
                str1[zhizhen6] = str2[zhizhen6] = 0;
                sum++;
            } else if (str2[zhizhen6] < str2[zhizhen8]) {
                he = he + str2[zhizhen8];
                str1[zhizhen8] = str2[zhizhen8] = 0;
                sum++;
            } else if (str2[zhizhen6] == str2[zhizhen8]) {
                if (str1[zhizhen6] >= str1[zhizhen8]) {
                    he = he + str2[zhizhen6];
                    str1[zhizhen6] = str2[zhizhen8] = 0;
                    sum++;
                } else {
                    he = he + str2[zhizhen8];
                    str1[zhizhen8] = str2[zhizhen8] = 0;
                    sum++;
                }
            }
        } else if (str3[zhizhen6] > paishu && str3[zhizhen8] > paishu) {
            for (long long int i = zhizhen8; i < n; i++) {
                if (str3[i] <= paishu) {
                    he = he + str2[i];
                    str1[i] = str2[i] = 0;
                    sum++;
                    break;
                }
            }
        }
    }

    printf("%lld", he);
}