n=int(input())
l=[list(input().split()) for _ in range(n)]
# print(l)
lst=[]
for i in range(n):
    tmp=[]
    for j in range(n):
        tmp.append(l[j][i])
    lst.append(tmp)
# print(lst)
ans_lst=[]
for k in range(n):
    cnt=0
    for kk in range(n):
        if k==kk:continue
        if lst[k][kk]=="nyanpass":cnt+=1
    if cnt==n-1:ans_lst.append(k+1)
print(ans_lst[0] if len(ans_lst)==1 else -1)