M=10**9+7
L=int(input())
ans=1
for i in range(L):
	P,e=map(int,input().split())
	R=pow(P-1,M-2,M)
	X=pow(P,e,M)
	ans*=(R*((((X+(R*(X-1))%M)*P)%M-(e+1))%M))%M
	ans%=M
print((ans+M)%M)