package contest; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class N408_4 { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(), m = ni(); int[] from = new int[m]; int[] to = new int[m]; for(int i = 0;i < m;i++){ from[i] = ni()-1; to[i] = ni()-1; } int[][] g = packU(n, from, to); int[] ff = new int[2*m]; int[] tt = new int[2*m]; int p = 0; for(int e : g[0]){ for(int ee : g[e]){ if(ee != 0){ ff[p] = ee; tt[p] = e; p++; } } } int[][] gg = packD(n, ff, tt, p); for(int[] row : gg){ Arrays.sort(row); } for(int i = 0;i < m;i++){ if(gg[from[i]].length >= 3 && gg[to[i]].length >= 2){ out.println("YES"); return; } if(gg[from[i]].length >= 2 && gg[to[i]].length >= 3){ out.println("YES"); return; } } for(int i = 0;i < m;i++){ int F = from[i], T = to[i]; if(gg[F].length > gg[T].length){ int D = F; F = T; T = D; } for(int e : gg[F]){ if(e == T)continue; for(int f : gg[T]){ if(f == F)continue; if(e == f)continue; out.println("YES"); return; } } } out.println("NO"); } public static int[][] packD(int n, int[] from, int[] to, int sup) { int[][] g = new int[n][]; int[] p = new int[n]; for(int i = 0;i < sup;i++)p[from[i]]++; for(int i = 0;i < n;i++)g[i] = new int[p[i]]; for(int i = 0;i < sup;i++){ g[from[i]][--p[from[i]]] = to[i]; } return g; } static int[][] packU(int n, int[] from, int[] to) { int[][] g = new int[n][]; int[] p = new int[n]; for (int f : from) p[f]++; for (int t : to) p[t]++; for (int i = 0; i < n; i++) g[i] = new int[p[i]]; for (int i = 0; i < from.length; i++) { g[from[i]][--p[from[i]]] = to[i]; g[to[i]][--p[to[i]]] = from[i]; } return g; } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new N408_4().run(); } private byte[] inbuf = new byte[1024]; private int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }