N = int(input())
A = [input().split() for _ in range(N)]

rntnp = []
for j in range(N):
    cnt = 0
    for i in range(N):
        if A[i][j] == 'nyanpass':
            cnt += 1
    if cnt == N-1:
        rntnp.append(j)

if len(rntnp) == 1:
    print(rntnp[0]+1)
else:
    print(-1)