#include<bits/stdc++.h>//万能头文件

using namespace std;

//注意大数组在放到main函数外边
int const maxN = 2000001;
int arr[maxN] = {0};

int main() {
    int n=0;
    cin >> n;
    double a;
    int t;

    for (int i = 1; i <= n; i++) {
        cin >> a >> t;
        for (int k = 1; k <= t; k++) {
            int c = floor(a * k);
            arr[c] = abs(arr[c] - 1);
        }
    }
    for (int i = 1; i <= maxN; i++) {
        if (arr[i] == 1) {
            cout << i << endl;
            break;
        }
    }
    return 0;
}