color = [0] * n
flag = True

def dfs(v, c):
	color[v] = c
	if c == 1:
		c = 2
	else:
		c = 1
	for u in range(n):
		if a[v][u] == 1:
			if color[u] != 0 and color!=c:
				flag = False
			if color[u] == 0:
				dfs(u, c)