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

ans = -1
for i in range(N):
    flag = True
    for j in range(N):
        if not(A[j][i] == "-" or A[j][i] == "nyanpass"):
            flag = False
            break
    if flag and ans > 0:
        ans = -1
        break
    if flag:
        ans = i + 1
print ans