from itertools import permutations
N = int(input())
P = [tuple(map(int, input().split())) for _ in range(N)]
ans = N*~-N//2
for p in permutations(P):
    ng = 0
    for i in range(N-1):
        if p[i][1] < p[-~i][0]:
            ng |= 1
    ans -= ng
print(ans)