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

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

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