#include<queue>
#include<math.h>
#include<stdio.h>
#include<iostream>
#include<vector>
#include<iomanip>
#include<string.h>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<utility>
#include<cstring>
#include<stack>
#include<fstream>
#include<string>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int n , t , ans = 0;
double a;
int main()
{
	cin >> n;
	for ( int i = 1 ; i <= n ; i++ )
	{
		cin >> a >> t;
		for ( int j = 1 ; j <= t ; j++ )
		{
			ans = ans ^ int( a * j );
		}
	}
	cout << ans;
	return 0;
}