package puzzle.yukicoder.golympic;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Scanner;
import java.util.Set;

public class Golympic {

    /* 頂点1から長さ5の単純閉路がある=頂点1から同一の頂点に対し、2Stepで行くルートと3Stepで行くルートが存在し、その途中にある頂点が重複していない */
    public static void main(String[] args) {
        FastScanner cin = new FastScanner(System.in);
        int n = cin.nextInt();
        int m = cin.nextInt();
        List<Integer>[] sideListArray = new List[n];
        for (int i = 0; i < m; i++) {
            int a = cin.nextInt() - 1;
            int b = cin.nextInt() - 1;
            if (sideListArray[a] == null) {
                sideListArray[a] = new ArrayList<Integer>();
            }
            sideListArray[a].add(b);
            if (sideListArray[b] == null) {
                sideListArray[b] = new ArrayList<Integer>();
            }
            sideListArray[b].add(a);
        }
        List<Integer>[] twoStepHistoriesArray = new List[n];
        for (int i : sideListArray[0]) {
            for (int j : sideListArray[i]) {
                if (j == 0) {
                    /* 頂点1に戻るルートだけは除外 */
                    continue;
                }
                if (twoStepHistoriesArray[j] == null) {
                    twoStepHistoriesArray[j] = new ArrayList<Integer>();
                }
                twoStepHistoriesArray[j].add(i);
            }
        }
        Set<Integer> set = new HashSet<Integer>(4);
        for (int i = 0; i < twoStepHistoriesArray.length; i++) {
            if (twoStepHistoriesArray[i] == null) {
                continue;
            }
            /* 3STEP目で行ける頂点のうち、2TEP目でも行けたものを探す */
            for (int j : sideListArray[i]) {
                if (twoStepHistoriesArray[j] == null) {
                    continue;
                }
                for (int twoStepHistory : twoStepHistoriesArray[i]) {
                    for (int otherTwoStepHistory : twoStepHistoriesArray[j]) {
                        /* 重複した頂点を通らないかはSetに全て格納、1以外の4頂点がaddできていればOK */
                        set.clear();
                        set.add(i);
                        set.add(j);
                        set.add(twoStepHistory);
                        set.add(otherTwoStepHistory);
                        if (set.size() == 4) {
                            exit(true);
                        }
                    }
                }
            }
        }
        /* 全探索を終えてもみつからなければ、無し。 */
        exit(false);
    }

    private static void exit(boolean result) {
        if (result) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }
        System.exit(0);
    }
    
    static class FastScanner {
        private final InputStream in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        public FastScanner(InputStream in) {
            this.in = in;
        }

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        public boolean hasNext() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }

        public int nextInt() {
            long nl = nextLong();
            if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
                throw new NumberFormatException();
            return (int) nl;
        }

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