N = int(input())
ck = [0 for i in range(100)]

for i in range(N):
    l = list(map(str, input().split()))
    for i in range(N):
        if l[i] == "nyanpass":
            ck[i] += 1

if ck.count(N-1):
    if ck.count(N-1) == 1:
        print(ck.index(N-1)+1)   
    else:
        print("-1")
else:
    print("-1")