def isin(a, b):
    if b >= a[0] and b <= a[1]:
        return 1
    else:
        return 0


def choose(minnum,maxnum, l):
    s = 0
    chose = []
    for i in range(minnum,maxnum):
        for j in range(len(l)):
            s = s + isin(l[j], i)
        chose.append(s)
        s = 0
    index = chose.index(max(chose))
    num = minnum+index
    new = []
    new1=[]
    new2=[]
    for j in range(len(l)):
        if not isin(l[j], num):
            new.append(l[j])
            new1.append(l[j][0])
            new2.append(l[j][1])
    return [new,new1,new2]
def delete(l,l1,l2):
    jh = 0
    delete = []
    for j in range(len(l)):
        for i in range(len(l1)):
            if l1[i] <= l[j][0] <= l2[i] or l1[i] <= l[j][1] <= l2[i]:
                jh = jh + 1
        if jh == 1:
            delete.append(l[j])
        jh = 0
    for i in range(len(delete)):
        l.remove(delete[i])
        l1.remove(delete[i][0])
        l2.remove(delete[i][1])
    return len(delete)


n = int(input())
l = []
l1=[]
l2=[]
for i in range(n):
    x = list(map(int, input().split()))
    l1.append(x[0])
    l2.append(x[1])
    l.append(x)
k=0
while len(l) > 0:
    k=k+delete(l,l1,l2)
    while len(l)>0:
        answer = choose(min(l1),max(l2), l)
        l=answer[0]
        l1=answer[1]
        l2=answer[2]
        k = k + 1
print(k-1)