import java.util.Calendar;
import java.util.Scanner;

class Main {
    static boolean[] visited;
    static int[][] edges;
    static int[][] vertices;
    static int count=0;
    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int m=s.nextInt();
        s.nextLine();
        visited=new boolean[n];
        edges=new int[m][2];
        vertices=new int[n][2];
        String[] str=new String[2];
        for (int i = 0; i < m; i++) {
            if(s.hasNext()){
                str=s.nextLine().split(" ");
                edges[i][0]=Integer.parseInt(str[0])-1;
                edges[i][1]=Integer.parseInt(str[1])-1;
                //edges[i+m][0]=Integer.parseInt(str[1])-1;
                //edges[i+m][1]=Integer.parseInt(str[0])-1;
            }
        }
        for (int i = 0; i < n; i++) {
            //visited=new boolean[n];
            explore(i);
        }
        /*for (int i = 0; i < n; i++) {
            System.out.println("Time for "+i+" is "+vertices[i][0]+" ||| "+vertices[i][1]);
        }*/
        for (int i = 0; i < edges.length; i++) {
            if(vertices[edges[i][1]][0]<vertices[edges[i][0]][0]&&vertices[edges[i][1]][1]>vertices[edges[i][0]][1]){
                System.out.println(1);
                System.exit(0);
            }

        }
        System.out.println(0);
    }

    private static  void  explore(int v) {

        visited[v]=true;
        if(vertices[v][0]==0)
            vertices[v][0]=++count;
        for (int i = 0; i < edges.length; i++) {
            if (edges[i][0]==v){
                if (visited[edges[i][1]]==false){
                    explore(edges[i][1]);
                /*}else{
                    System.out.println(1);
                    System.exit(0);*/
                }
            }
        }
        if(vertices[v][1]==0)
            vertices[v][1]=++count;

    }
}