def EdgesCounter(Array):
    edge = 0
    for i in range (len(Array)):
        for j in range (i, len(Array)):
            if Array[i][j] == 1:
                edge += 1
    return edge

def FillMatrix(rng):
    Array = []
    for i in range (rng):
        Array.append(list(map(int, input().split())))
    return Array

Matrix = FillMatrix(int(input()))

print(EdgesCounter(Matrix))