import std.conv, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = cast(int)(as.length); for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; }
int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a < val)); }
int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) => (a <= val)); }


import std.bitmanip : BitArray;

int N, M;
int[] A, B;

void main() {
  try {
    for (; ; ) {
      N = readInt();
      M = readInt();
      A = new int[M];
      B = new int[M];
      foreach (i; 0 .. M) {
        A[i] = readInt() - 1;
        B[i] = readInt() - 1;
      }
      
      auto g = new BitArray[N];
      foreach (u; 0 .. N) {
        g[u].length = N;
      }
      foreach (i; 0 .. M) {
        g[A[i]][B[i]] = true;
        g[B[i]][A[i]] = true;
      }
      auto vs = new int[][N];
      foreach (u; 1 .. N) {
        g[u] &= g[0];
        vs[u] = g[u].bitsSet.take(3).array.to!(int[]);
        debug {
          writeln(u, ": ", vs[u]);
        }
      }
      
      bool ans;
      foreach (i; 0 .. M) {
        foreach (va; vs[A[i]]) foreach (vb; vs[B[i]]) {
          if (va != vb && va != B[i] && vb != A[i]) {
            ans = true;
          }
        }
      }
      writeln(ans ? "YES" : "NO");
    }
  } catch (EOFException e) {
  }
}