#include<stdio.h>

int main() {
	int n; double a; int b; int cnt;
	int sum; int sum1[200010] = { 0 };
	scanf_s("%d", &n);
	for (int i = 1; i <= n; i++) {
		scanf_s("%lf %d", &a, &b);
		for (double j = 1.00; j <= b; j++) {
			sum = (int)(a * j);
			if (sum1[sum] == 1) {
				sum1[sum] = 0;
			}
			else {
				sum1[sum] = 1;
			}
		}
	}
	for (int k = 1; k <= 2000000; k++) {
		if (sum1[k] == 1) {
			cnt = k;
			printf("%d", cnt);
			return 0;
		}
	}
}