import sys
input = sys.stdin.readline

L = int(input())
ans = 1
MOD = 10**9+7
inv = lambda x: pow(x, MOD-2, MOD)

for _ in range(L):
    P, e = map(int, input().split())
    ans *= inv(P-1)*(P*(pow(P, e+1, MOD)-1)*inv(P-1)%MOD-(e+1))%MOD
    ans %= MOD

print(ans)