C

#include <iostream>

int main() {
    int a;
    std::cin>>a;
    int map[a][a];


    for (int x = 0; x < a; x++)
        for (int y = 0; y < a; y++)
            std::cin>>map[x][y];

    int c = 0;

    for (int y = 0; y < a; y++)
        for (int x = 0; x < y; x++)
            if (map[x][y] == 1) {
                c++;
            }

    std::cout<<c;
    return 0;
}