diagonal.py

#!/usr/bin/env python3


def diagonal_principal(m):
    ac = 0
    m1 = []
    while ac <= len(m) - 1:
        vet = m[ac]
        m1.append(vet[ac])
        ac += 1
    return sum(m1)


def diagonal_secundaria(m):
    dec = len(m) - 1
    aux = 0
    m2 = []
    while dec >= 0:
        vet = m[aux]
        m2.append(vet[dec])
        dec -= 1
        aux += 1
    return sum(m2)


if __name__ == '__main__':
    d = int(input())
    m = []
    for r in range(0, d):
        matrix = list(map(int, input().split()))
        m.append(matrix)
    d_prin = diagonal_principal(m)
    d_sec = diagonal_secundaria(m)
    print(d_prin - d_sec)