X = "nyanpass"
N = int(input())
B = [set() for _ in range(N)]
for i in range(N):
    A = list(map(str, input().split()))
    for j in range(N):
        if i != j:
            B[j].add(A[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)