from sys import stdin
import re
import sys

line = stdin.readline()
n = int(line)

assert 2 <= n and n <= 2500

arr = []

for i in xrange(n):
    line = stdin.readline()
    row = map(int, line.strip().split())
    arr.append(row)

print("here")

for i in xrange(n):
    for j in xrange(n):
        if i == j:
            assert arr[i][j] == 0
        else:
            assert 1 <= arr[i][j] and arr[i][j] < 10000000
            assert arr[i][j] == arr[j][i]

sys.exit(42)