#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;
int n;
ll a, b, ansa = 0, ansb = 1, na, nb;
ll mod = 1000000007;
ll pw(ll x, ll k){
if(k == 0) return 1;
if(k == 1) return x;
ll t = pw(x, k / 2); t *= t; t %= mod;
if(k % 2) return t * x % mod;
return t;
}
ll modinv(ll x){
return pw(x, mod - 2);
}
int main(){
scanf("%d", &n);
for(int i = 0; i < n; i++){
scanf("%lld%lld", &a, &b);
na = b * ansb + a * ansa;
nb = a * ansb;
ansa = na / __gcd(na, nb);
ansb = nb / __gcd(na, nb);
}
printf("%lld\n", (ansa * modinv(ansb)) % mod);
}
