import java.util.*;
import java.lang.*;
import java.io.*;

// The main method must be in a class named "Main".
class Main {
    public static void main(String[] args) throws IOException{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        int N, M;
        StringTokenizer st = new StringTokenizer(br.readLine());
        N = Integer.parseInt(st.nextToken());
        M = Integer.parseInt(st.nextToken());

        ArrayList<Integer>[] graph = new ArrayList[N];
        for (int i=0; i<N; i++) {
            // graph[i].add(new ArrayList<Integer>());
            // graph[i]는 정수를 받음을 생각할 수 있다.
            graph[i] = new ArrayList<>();
        }
        
        int[] connected = new int[N];
        for (int i=0; i<M; i++) {
            st = new StringTokenizer(br.readLine());
            int a = Integer.parseInt(st.nextToken())-1;
            int b = Integer.parseInt(st.nextToken())-1;
            graph[a].add(b);
            connected[b] ++;
        }
        
        Queue<Integer> q = new ArrayDeque<>();
        for (int i=0; i<N; i++) {
            if (connected[i] == 0) {
                q.add(i);
            }
        }

        int dealed_num = 0;
        
        while (!q.isEmpty()) {
            int now = q.poll();
            dealed_num ++;
            for (int next : graph[now]) {
                connected[next] --;
                if (connected[next] == 0) {
                    q.add(next);
                }
            }
        }
        System.out.println(dealed_num==N ? "No" : "Yes");     
        
        
        
    }
}