import sys
readline=sys.stdin.readline

N=int(readline())
A=[readline().split() for i in range(N)]
ans_lst=[]
for j in range(N):
    if all(A[i][j]=="nyanpass" for i in range(N) if i!=j):
        ans_lst.append(j+1)
if len(ans_lst)==1:
    ans=ans_lst[0]
else:
    ans=-1
print(ans)