E-sport

#include <iostream>
#include <vector>

using namespace std;
int visited[100010];
bool error;
vector<int>  esport[100010];
bool compet(int x)
{
    if(visited[x]==1)
    {
        return true;
    }
    if(visited[x]==2)
    {
        return false;
    }
    visited[x]=1;
    for(auto c : esport[x])
    {
        if(compet(c))
        {
            return true;
        }
    }
    visited[x]=2;
    return false;

}

int main()
{
    int n,m;
    cin >> n >> m;
    int u,v;
    for(int i=0; i<m; ++i)
    {
        cin >> u >> v;
        esport[u].push_back(v);
    }


    for(int i=1; i<=n; ++i)
    {
        if(visited[i]!=2)
        {
            if(compet(i))
            {
                error=true;

            }
        }
    }

    if(error)
    {
        cout << "Yes";
    }
    else
    {
        cout << "No";
    }

    return 0;
}