#include<iostream>
using namespace std;

int main() {
	int n;
	cin >> n;
	bool arr[6000];
	memset(arr, false, sizeof(arr));
	double a;
	int t;
	for (int i = 0; i < n; i++) {
		cin >> a >> t;

		for (int j = 1; j <= t; j++) {
			int res = (int)(a * j);
			if (arr[res] == true)arr[res] = false;
			else arr[res] = true;
		}

	}
	for (int i = 1; i < 6000; i++) {
		if (arr[i] == true) {
			cout << i;
			break;
		}
	}
	return 0;
}