N = int(input())
A = [input().split() for _ in range(N)]

rentyonpoi = []
for i in range(N):
    gr = [a[i] for a in A]
    nyanpass_cnt = gr.count("nyanpass")
    if nyanpass_cnt == N - 1:
        rentyonpoi.append(i)

if (len(rentyonpoi) == 1):
    print(rentyonpoi[0] + 1)
else:
    print(-1)