import std.stdio;
import std.algorithm;
import std.typecons;
import std.string;
import std.array;
import std.conv;
import std.container;

void main() {
    int N, M;
    readf("%d %d\n", &N, &M);
    alias E = Tuple!(int, int);
    bool[E] es;
    auto G = new int[][](N);
    foreach (i; 0 .. M) {
        int a, b;
        readf("%d %d\n", &a, &b);
        a--; b--;
        G[a] ~= b;
        G[b] ~= a;
        if (a > b) swap(a, b);
        es[E(a, b)] = true;
    }

    alias S = Tuple!(int, "index", int, "depth", int, "prev");
    alias P = Tuple!(int, "v", int, "prev");
    bool[S] D;
    D[S(0, 0, -1)] = true;
    P[] X;
    DList!S Q;
    Q.insert(S(0, 0, -1));
    while (!Q.empty) {
        auto c = Q.front; Q.removeFront;
        int v = c[0];
        int d = c[1];
        int prev = c[2];
        if (d == 2) {
            X ~= P(v, prev);
            continue;
        }
        foreach (nv; G[v]) {
            if (nv == prev) continue;
            int nd = d + 1;
            if (S(nv, nd, v) in D) continue;
            D[S(nv, nd, v)] = true;
            Q.insert(S(nv, nd, v));
        }
    }
    for (auto i = 0; i < X.length; i++) {
        for (auto j = i + 1; j < X.length; j++) {
            int u = X[i].v;
            int v = X[j].v;
            if (u > v) swap(u, v);
            if (E(u, v) !in es) continue;
            auto vs = [u, v, X[i].prev, X[j].prev];
            bool flag = true;
            foreach (a; 0 .. 4) {
                foreach (b; 0 .. 4) {
                    if (a == b) continue;
                    if (vs[a] == vs[b]) {
                        flag = false;
                    }
                }
            }
            if (flag) {
                writeln("YES");
                return;
            }
        }
    }
    writeln("NO");
}