N = int(input())
A = []
for i in range(N):
    A.append(0)
for i in range(N):
    B = list(input().split())
    for c in range(N):
        if B[c] == "nyanpass":
            A[c] += 1
if A.count(N-1) == 1:
    for i in range(N):
        if A[i] == N-1:
            print(i+1)
else:
    print(-1)