n=int(input())
a=[list(input().split()) for _ in range(n)]
b=[]
for i in range(n):
    ok=True
    for j in range(n):
        ok&=a[i][j]=='nyanpass' or i==j
    if ok :
        b.append(i+1)
if len(b)==1:
    print(b[0])
else:
    print(-1)