N = int(input())

greeting_table = [
    input().split() for _ in range(N)
]
renchons = [
    i for i, greets in enumerate(zip(*greeting_table), start=1)
    if all(elem in ('nyanpass', '-') for elem in greets)
]

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