#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;
}