#include<bits/stdc++.h>  
using namespace std;
int lamp[200001]={0};
int main()
{
    int time,t,i,j;
    float a;
    cin>>time;
    for(i=1;i<=time;i++)
	{
        cin>>a>>t;
        for (j=1;j<=t;j++)
		{
            lamp[(int)(a*j)]++;
        }
    }
    i=1;
    while(lamp[i]%2==0)
	{
        i++;
    }
      cout<<i;    
	    return 0;
}