n = int(input())

LS = []
for i in range(n):
    LS.append(input().split())


num = 0
N = n
for i in range(n):
    cnt = 0
    for j in range(N):
        if LS[j][i] == 'nyanpass':
            cnt += 1
    if cnt == n-1:
        num += 1

if num == 1:
    print("1")
else: 
    print(-1)