N = int(input())
ls = [input().split() for i in range(N)]
cntN = [0]*N
for i in range(N):
    for j in range(N):
        if i == j:
            continue
        if ls[i][j] == 'nyanpass':
            cntN[j] += 1

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