N = int(input())
Rng = range(N)
nyanpass = [0] * N
for i in Rng:
    A = list(input().split())
    for j in Rng:
        if A[j] == 'nyanpass':
            nyanpass[j] += 1

cnt = 0
for j in Rng:
    if nyanpass[j] == N - 1:
        cnt += 1
        ans = (j + 1)
    if cnt > 1:
        break

if cnt == 1:
    print(ans)
else:
    print(-1)