N = int(input())
A = [[0]] * N

for i in range(N):
    A[i] = input().split()

tokutei = []
for j in range(N):
    for i in range(N):
        ren = True
        if i == j:
            continue
        elif A[i][j] != "nyanpass":
            ren = False
            break
    if ren:
        tokutei.append(j)

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