#include<iostream>
using namespace std;
int i,j;
bool light[10009];
int main () {
    int n;
    cin>>n;
    double a;
    int t;
    for (int i = 1; i <= n; i++) {
        cin >>a>>t;
        for (int j = 1; j <= t; i++) {
            if (light[(int)(t*i)] == true) {
                light[(int)(t*i)] = false;
            }
            else {
                light[(int)(t*i)] = true;
            }
        }
    }
    for (i = 1; i <= 10000; i++) {
        if (light[i] == true) {
            cout << i << endl;
            break;
        }
    }
    return 0;
}