import java.io.*;
import java.util.*;


public class Main_yukicoder408 {

    public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
    	Printer pr = new Printer(System.out);

    	int n = sc.nextInt();
    	int m = sc.nextInt();

    	List<List<Integer>> edges = new ArrayList<>(n);
    	for (int i = 0; i < n; i++) {
    		edges.add(new ArrayList<>());
    	}

    	for (int i = 0; i < m; i++) {
    		int a = sc.nextInt() - 1;
    		int b = sc.nextInt() - 1;

    		edges.get(a).add(b);
    		edges.get(b).add(a);
    	}

    	Deque<List<Integer>> st = new ArrayDeque<>();
    	List<Integer> hs = new ArrayList<>();
    	hs.add(0);
    	st.push(hs);

    	while (!st.isEmpty()) {
    		List<Integer> e = st.pop();

    		if (e.size() == 5) {
    			if (edges.get(e.get(e.size() - 1)).contains(0)) {
    				pr.println("YES");

    				pr.close();
    				sc.close();
    				return;
    			}
    		} else {
    			for (int next : edges.get(e.get(e.size() - 1))) {
    				if (!e.contains(next)) {
    					List<Integer> tmp = new ArrayList<>(e);
    					tmp.add(next);
    					st.push(tmp);
    				}
    			}
    		}
    	}

    	pr.println("NO");

        pr.close();
        sc.close();
    }

	@SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
//					it = Arrays.asList(br.readLine().split(" ")).iterator();
					it = Arrays.asList(br.readLine().split("\\p{javaWhitespace}+")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}