n=int(input())
ans=[0]*n
for i in range(n):
    a=list(input().split())
    for j in range(n):
        if a[j]=="nyanpass":
            ans[j]+=1
if ans.count(n-1)==1:
    for i in range(n):
        if ans[i]==n-1:
            print(i+1)
            break
else:
    print(-1)