R = set(['nyanpass', '-'])
n = int(input())

greetings = []
for i in range(n):
    greetings.append(input().split())

result = []
for i, col in enumerate(zip(*greetings)):
    if R == set(col):
        result.append(i)

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