#include<iostream>
#include<vector>

using namespace std;

int n, t,len=0;
float a;
vector<int> ming;

int main()
{
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> a >> t;
		int m = int(a*t);
		if (m > len) len= m;
		for (int j = 1; j <=t; j++)
		{
			ming.push_back(int(j*a));
		}
	}
	vector<int> lamp(len+1, 0);
	for (int j = 0; j < ming.size(); j++)
	{
			lamp[ming[j]] = 1 - lamp[ming[j]];
	}
	for (int i = 1; i <= len; i++)
	{
		if (lamp[i] == 1)
		{
			cout << i;
			break;
		}
	}
	return 0;
}