#include<iostream>
#include<cmath>
using namespace std;

int main() {
    int n, ans[2000010] = {0}, t;
    double a;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a >> t;
        for (int j = 0; j < t; j++) {
            if (ans[int(j*a)] == 1) ans[int(j*a)] = 0;
            else ans[int(j*a)] = 1;
        }
    }
    for (int k = 0; k < 2000000; k++) {
        if (ans[k]) {
            cout << k << endl;
            return 0;
        }
    }
}