#include<stdio.h>
int a[2000001];
int main() {
    int n;
    double x, y;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        scanf("%lf %lf", &x, &y);
        for (double k = 1; k <= y; k++) {
            int u = x * k;
            if (a[u] == 0) a[u] = 1;
            if (a[u] == 1) a[u] = 0;
        }
    }for (int m = 0;; m++) {
        if (a[m] == 1) {
            printf("%d", m);
            break;
        }
    }
    return 0;
}