#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */
    int size =0;
    cin >> size;
     vector< vector<int> > matrix(size, vector<int>(size));
    for (int i = 0; i < size; ++i) {
        for (int j = 0; j < size; ++j) {
            int num;
            cin >> num;
            matrix[i].push_back(num);
        }
    }
    int first = 0;
    int second = 0;

    for (int i = 0; i < size; ++i) {
        first += matrix[i][i];
    }
    int i = size - 1;
    int j = 0;
    for (; i >= 0; --i) {
        second += matrix[j][i];
        ++j;
    }
    int total = first-second;
    cout << total;
    return 0;
}