n = int(input())
a = []
for _ in range(n):
    a_ = list(input().split())
    a.append(a_)

cnt = [True] * n
for i in range(n):
    for j in range(n):
        if i == j:
            continue
        if a[i][j] != "nyanpass":
            cnt[j] = False

if sum(cnt) == 1:
    print(cnt.index(True)+1)
else:
    print(-1)