Codeforces Beta Round 88
C
Cycle
Codeforces
2000
原题
← BD →
翻译中…

A tournament is a directed graph without self-loops in which every pair of vertexes is connected by exactly one directed edge. That is, for any two vertexes $*u*$ and $*v*$ ($*u* ≠ *v*$) exists either an edge going from $*u*$ to $*v*$, or an edge from $*v*$ to $*u*$.

翻译中…

You are given a tournament consisting of $*n*$ vertexes. Your task is to find there a cycle of length three.

翻译中…

Input

翻译中…

The first line contains an integer $*n*$ ($1 ≤ *n* ≤ 5000$). Next $*n*$ lines contain the adjacency matrix $*A*$ of the graph (without spaces). $*A*_{*i*, *j*} = 1$ if the graph has an edge going from vertex $*i*$ to vertex $*j*$, otherwise $*A*_{*i*, *j*} = 0$. $*A*_{*i*, *j*}$ stands for the $*j*$-th character in the $*i*$-th line.

翻译中…

It is guaranteed that the given graph is a tournament, that is, $*A*_{*i*, *i*} = 0, *A*_{*i*, *j*} ≠ *A*_{*j*, *i*}$ $(1 ≤ *i*, *j* ≤ *n*, *i* ≠ *j*)$.

翻译中…

Output

翻译中…

Print three distinct vertexes of the graph $*a*_{1}$, $*a*_{2}$, $*a*_{3}$ ($1 ≤ *a*_{*i*} ≤ *n*$), such that $*A*_{*a*_{1}, *a*_{2}} = *A*_{*a*_{2}, *a*_{3}} = *A*_{*a*_{3}, *a*_{1}} = 1$, or "-1", if a cycle whose length equals three does not exist.

翻译中…

If there are several solutions, print any of them.

翻译中…

样例

Input #1
5
00100
10000
01001
11101
11000
Output #1
1 3 2
InputCopy OutputCopy
Input #2
5
01111
00000
01000
01100
01110
Output #2
-1
InputCopy OutputCopy
题目信息
题号
117C
时间限制
2.5 s
内存限制
256 MB
标签
DFS 及类似
图论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。