MOD = 10 ** 9 + 7
l = int(input())
ans = 1
for i in range(l):
    p, e = map(int, input().split())
    ans *= (p * (pow(p, e + 1, MOD) - 1) - p * (e + 1) + (e + 1)) * pow((p - 1) * (p - 1), MOD - 2, MOD)
    ans %= MOD
print(ans)