# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	D = defaultdict(int)
	A = []
	for i in range(N):
		a = list(input().split())
		A.append(a)
	for i in range(N):
		jud = 1
		for j in range(N):
			if i != j:
				if A[j][i] != "nyanpass":
					jud = 0
					break

		if jud == 1:
			D[i + 1] = 1

	if len(D) == 0 or len(D) >= 2:
		print(-1)

	else:
		for i in D:
			print(i)



if __name__ == '__main__':
	main()