N = int(raw_input())
REN = "nyanpass"
nps = [[0,i] for i in range(N)]
for i in range(N):
	v = raw_input().split(" ")
	for j in range(N):
		if v[j] == REN:
			nps[j][0] += 1
nps.sort()
print nps[-1][1] + 1 if nps[-1][0] == N-1 and nps[-2][0] < N-1 else -1