N = int(input())
A = [[0 for i in range(N)] for j in range(N)]

for i in range(N):
    A_ij = input().split()
    for j in range(N):
        A[i][j] = A_ij[j]

rentyon_ppoi_list = []
for j in range(N):
    flag = True
    for i in range(N):
        if i == j:
            pass
        elif A[i][j] == "nyanpass":
            pass
        else:
            flag = False
    if flag:
        rentyon_ppoi_list.append(j+1)

if(len(rentyon_ppoi_list) == 1):
    print(int(rentyon_ppoi_list[0]))
else:
    print(-1)