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using System.Collections.Generic;
class Graph
{
private int V; // No. of vertices
private List<int>[] adj; // Adjacency List
public Graph(int v)
{
V = v;
adj = new List<int>[V];
for (int i = 0; i < V; ++i)
adj[i] = new List<int>();
}
// Function to add an edge into the graph
public void addEdge(int v, int w)
{
adj[v].Add(w);
}
// A recursive function that uses visited[] and parent to detect
// cycle in subgraph reachable from vertex v.
private bool isCyclicUtil(int v, bool[] visited, bool[] recStack)
{
if (recStack[v])
return true;
if (visited[v])
return false;
visited[v] = true;
recStack[v] = true;
List<int> children = adj[v];
foreach (int c in children)
if (isCyclicUtil(c, visited, recStack))
return true;
recStack[v] = false;
return false;
}
// Returns true if the graph contains a cycle, else false.
public bool isCyclic()
{
// Mark all the vertices as not visited and not part of
// recursion stack
bool[] visited = new bool[V];
bool[] recStack = new bool[V];
// Call the recursive helper function to detect cycle in
// different DFS trees
for (int i = 0; i < V; i++)
if (isCyclicUtil(i, visited, recStack))
return true;
return false;
}
}
class Program
{
static void Main(string[] args)
{
int N, M;
string[] NM = Console.ReadLine().Split();
N = int.Parse(NM[0]);
M = int.Parse(NM[1]);
Graph g = new Graph(N);
for (int i = 0; i < M; i++)
{
string[] uv = Console.ReadLine().Split();
int u = int.Parse(uv[0]) - 1;
int v = int.Parse(uv[1]) - 1;
g.addEdge(u, v);
}
// Check if reversing one edge can create a cycle
for (int i = 0; i < M; i++)
{
string[] uv = Console.ReadLine().Split();
int u = int.Parse(uv[0]) - 1;
int v = int.Parse(uv[1]) - 1;
g.addEdge(v, u);
if (g.isCyclic())
{
Console.WriteLine("Yes");
return;
}
g.adj[v].Remove(u); // Remove the added edge
}
Console.WriteLine("No");
}
}
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