n = int(input())
L = [list(input().split()) for _ in range(n)]

ans = -1
for j in range(n):
    flag = True
    for i in range(n):
        if i == j:
            continue
        if L[i][j] != "nyanpass":
            flag = False
            break
    if flag:
        if ans == -1:
            ans = j + 1
        else:
            ans = -1
            break
print(ans)