N = int(input())

x = [0] * N
for i in range(N):
    A = input().split()
    for j in range(N):
        if A[j] == 'nyanpass':
            x[j] += 1

if len([a for a in x if a == (N-1)]) == 1:
    print(x.index(N-1) + 1)
else:
    print(-1)