X = "nyanpass"
N = int(input())
A = [[] for __ in range(N) ]

B = [set() for _ in range(N)]
for i in range(N):
    A[i] = list(map(str, input().split()))


for i in range(N):
    for j in range(N):
        if i != j:
            B[j].add(A[i][j])
            
ANS = []
for j in range(N):
    if len(B[j])==1 and X in B[j]:
        ANS.append(j)

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