n=int(input())
ans=[0]*n;f_ans=[]
for i in range(n):
    s=input().split()
    for j in range(len(s)):
        if s[j]=='nyanpass' or s[j]=='-':
            ans[j]+=1
for i in range(len(ans)):
    if ans[i]==n:
        f_ans.append(i)
if len(f_ans)==1:
    print(f_ans[0]+1)
else:
    print(-1)