OI-codes/Luogu/P1161/P1161.cpp

// R36448353

#include <bits/stdc++.h>

using namespace std;

int main() {
    int n, t, ans;
    n = t = ans = 0;
    double a;
    n = t = ans = 0;
    cin >> n;
    for (int i = 1; i <= n; i++) {
        cin >> a >> t;
        for (int j = 1; j <= t; j++) {
            ans ^= int(j * a);
        }
    }
    cout << ans << endl;
    return 0;
}