N=int(input())
S=[input().split() for i in range(N)]

x="nyanpass"

ANS=[]

for i in range(N):
    for j in range(N):
        if i==j:
            continue
        if S[j][i]!=x:
            break
    else:
        ANS.append(i+1)

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