L = int(input())
MOD = 10 ** 9 + 7
modinv = lambda a, mod=MOD: pow(a, mod - 2, mod)

ans = 1
for _ in range(L):
    P, E = map(int, input().split())
    pi = modinv(P - 1)
    ans *= ((pow(P, E + 2, MOD) - 1) * pi - 1 - (E + 1)) * pi % MOD
    ans %= MOD
print(ans)