#include <cstdio>
#define N 200009
#define RI register int
#define Max(x, y) ((x) > (y) ? (x) : (y))
using namespace std;

const int P = 1e9 + 7;
int n, aa, bb, ans;

inline int read();
inline int fsq(int x, int tn, int ret = 1) {
    while (tn) {
        if (tn & 1)
            ret = 1ll * ret * x % P;
        x = 1ll * x * x % P;
        tn >>= 1;
    }
    return ret;
}
inline void ad(int x) {
    int fz = 1, fm = 1;
    for (RI i = 1; i <= x; ++i) fm = 1ll * fm * i % P, fz = 1ll * fz * (n - i + 1) % P;
    fm = fsq(fm, P - 2);
    fz = 1ll * fz * fm % P;
    fz = fz ? P - fz : 0;
    (ans += fz) %= P;
}

int main() {
    n = read();
    aa = read(), bb = read();
    ans = fsq(2, n);
    ad(aa);
    ad(bb);
    printf("%d\n", ans ? ans - 1 : P - 1);
    return 0;
}

inline int read() {
    int x = 0, fh = 1;
    char c = getchar();
    while (c > '9' || c < '0') fh = c == '-' ? -1 : fh, c = getchar();
    while (c >= '0' && c <= '9') {
        x *= 10;
        x += c - '0';
        c = getchar();
    }
    return x * fh;
}