#include <bits/stdc++.h>

using namespace std;
long long n, a, b, he, jian;

int main() {
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> a >> b;
        jian = jian + a + b - 8;
        he += jian;
    }
    cout << he << endl;
    return 0;
}