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

immutable int INF = 1 << 28;

void main() {
    auto s = readln.split.map!(to!int);
    auto N = s[0];
    auto M = s[1];
    auto edges = new int[][](N);
    foreach (i; 0..M) {
        s = readln.split.map!(to!int);
        edges[s[0] - 1] ~= s[1] - 1;
        edges[s[1] - 1] ~= s[0] - 1;
    }


    auto VU = new int[][](N);

    foreach (u; edges[0]) {
        foreach (v; edges[u]) {
            if (v != 0)
                VU[v] ~= u;
        }
    }


    bool ok = false;
    
    foreach (i; 1..N) {
        foreach (j; edges[i]) {
            if (VU[i].length == 0 || VU[j].length == 0) continue;
            if (VU[i].length == 1 && VU[j].length == 1 && VU[i][0] == VU[j][0]) continue;
            ok = true;
        }
    }

    writeln(ok ? "YES" : "NO");
}