#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
const int N = 10;

int n;
int a[N], m[N];

void exgcd(int a, int b, int &x, int &y) {
    if (!b)
        x = 1, y = 0;
    else {
        exgcd(b, a % b, y, x);
        y -= a / b * x;
    }
}

signed main() {
    cin >> n;
    int M = 1;

    for (int i = 1; i <= n; i++) {
        cin >> m[i] >> a[i];
        M *= m[i];
    }

    int res = 0, x, y;
    for (int i = 1; i <= n; i++) {
        exgcd(M / m[i], m[i], x, y);
        res += a[i] * M / m[i] * x;
    }

    cout << (res % M + M) % M << endl;
}