#include <algorithm>
#include <assert.h>
#include <complex>
#include <ctype.h>
#include <functional>
#include <iostream>
#include <limits.h>
#include <locale.h>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <vector>
#include <unordered_set>
#include <unordered_map>
#pragma warning(disable:4996)
using namespace std;
#define mp make_pair
typedef long long ll;
typedef unsigned long long ull;
typedef double db;
typedef long double ldb;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef pair <ll, int> pli;
typedef pair <ldb, ldb> pdd;
int IT_MAX = 131072;
const ll MOD = 1000000007;
const int INF = 1034567891;
const ll LL_INF = 2234567890123456789ll;
const db PI = 3.141592653589793238;
const ldb ERR = 1E-10;
ll mul_inv(ll a, ll b)
{
ll b0 = b, t, q;
ll x0 = 0, x1 = 1;
if (b == 1) return 1;
while (a > 1) {
q = a / b;
t = b, b = a % b, a = t;
t = x0, x0 = x1 - q * x0, x1 = t;
}
if (x1 < 0) x1 += b0;
return x1;
}
int main() {
int N, t1, t2;
scanf("%d", &N);
ll ans = 0;
while (N--) {
scanf("%d %d", &t1, &t2);
ans += (t2 * mul_inv(t1, MOD)) % MOD;
}
return !printf("%lld\n", ans%MOD);
}
