n = int(input())
T = [[""] * n for i in range(n)]
for i in range(n):
    a = list(input().split())
    for j in range(n):
        T[i][j] = a[j]

num = -1
for i in range(n):
    rec = 0
    for j in range(n):
        if T[j][i] == "nyanpass":
            rec += 1
    if rec == n - 1:
        if num == -1:
            num = i + 1
        else:
            num = -1
            break
print(num)