n=int(input())
a=[[str(i) for i in input().split()] for i in range(n)]

count=[0 for i in range(n)]
for i in range(n):
    for j in range(n):
        if i!=j and a[i][j]!='nyanpass':
            count[j]+=1

for i in range(n):
    if count[i]==0:
        print(i+1)
        break

if 0 not in count:
    print(-1)