N = int(input())
A = [True] * N
for i in range(N):
    for j, a in enumerate(input().split()):
        if i == j:
            continue
        if a != 'nyanpass':
            A[j] = False
if A.count(True) != 1:
    print(-1)
else:
    print(A.index(True) + 1)