23706번 - Dr. Bill Poucher 다국어

There are $n$ people. Each person sees some of the other people. Each of them will be given a black or white hat. After that each person will simultaneously name a color. Everyone who doesn't guess the color on his hat will die. Horribly. 

Is there a deterministic strategy which guarantees that at least one person will survive?       

The first line contains two integers $n$ and $m$ ($2 \leq n \leq 3 \cdot 10^5, 1 \leq m \leq 3 \cdot 10^5$), the number of people and the number of relations of seeing someone (see below), respectively.

$m$ lines follow. $i$-th of them contains two integers $a_i$ and $b_i$ ($0 \leq a_i, b_i <   n, a_i \neq b_i$) meaning that $a_i$-th person sees $b_i$-th person. For all $i \neq j$, $a_i \neq a_j$ or $b_i \neq b_j$ holds.

Print 1 if there exists such strategy and 0 otherwise.