N = int(input())
S = [[0 if c == '.' else 1 for c in input()]for i in range(N)]
def op(r, c):
	S[r][c] ^= 1
	S[r - 1][c] ^= 1
	S[r][c - 1] ^= 1
	S[r - 1][c - 1] ^= 1
	S[r][0] ^= 1
	S[r - 1][0] ^= 1
	S[r][-1] ^= 1
	S[r - 1][-1] ^= 1
	S[0][c] ^= 1
	S[-1][c] ^= 1
	S[0][c - 1] ^= 1
	S[-1][c - 1] ^= 1
ans = set()
for i in range(1, N):
	for j in range(1, N):
		if S[i][j]:
			ans ^= {(i, j)}
			op(i, j)
for i in range(1, N):
	if S[i - 1][0]:
		for j in range(1, N):
			ans ^= {(i, j)}
			op(i, j)
	if S[0][i - 1]:
		for j in range(1, N):
			ans ^= {(j, i)}
			op(j, i)
if S[0][0]:
	ans ^= {(0, 0)}
	op(0, 0)
if sum([sum(S[i]) for i in range(N)]):
	print(-1)
else:
	print(len(ans))
	for RC in ans:
		print(*RC)