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