#include<iostream>
#include<cmath>
#include<algorithm>
#include<iomanip>
using namespace std;
int a[200001] = { 0 };
int main()
{
	int n;
	double b, t;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		cin >> b >> t;
		for (int j = 1; j <= t; j++)
		{
			a[int(j*b)] = 1 - a[int(j*b)];
		}
	}
	for (int i = 1; ; i++)
	{
		if (a[i] == 1)
		{
			cout << i;
			break;
		}
	}
}