#include<iostream>
#include <vector>
#include <queue>
using namespace std;
const int INF = 1e3 + 5;
vector<bool> visited(INF,false);
vector<int> color(INF,-1);
bool bfs(int u,vector<vector<int>> &adj)
{
    queue<int> q;
    q.push(u);
    visited[u] = true;
    color[u] = 0;
    while(!q.empty())
    {
        int s = q.front();
        q.pop();
        for(int v:adj[s])
        {
            if(!visited[v] && color[v] == -1)
            {
                q.push(v);
                visited[v] = true;
                color[v] = color[s] ? 0: 1;
            }

            if(color[u] == color[v])

            {
                return 0;
            }
        }
    }
    return 1;
}
int main()
{
    int n,e;
    cin>>n>>e;
    vector<vector<int>> adj(n+1);
    while(e--)
    {
        int u,v;
        cin>>u>>v;
        adj[u].push_back(v);
    }
    bool result = bfs(2,adj);
    if (result)
        cout << "Yes\n";
      else
        cout << "No\n";
    return 0;
}