n = int(input())
ls = []
for i in range(n):
    ls.append(input().split())

res_list = []
for i in range(n):
    counter = 1
    for j in range(n):
        if (ls[j][i] != 'nyanpass') and (ls[j][i] != '-'):
            break
    else:
        res_list.append(i + 1)

if len(res_list) != 1:
    print(-1)
else:
    print(res_list[0])