#include <bits/stdc++.h>
using namespace std;

int n, m;
vector<int> g[20202];
bitset<20202> path[20202]; // last

bool solve() {
	cin >> n >> m;
	for (int i = 0; i < m; i++) {
		int u, v;
		scanf("%d %d", &u, &v);
		u--;
		v--;
		g[u].push_back(v);
		g[v].push_back(u);
	}

	for (int i : g[0]) {
		for (int j : g[i]) if (j != 0) {
			path[j][i] = true;
		}
	}

	for (int i = 1; i < n; i++) {
		for (int j : g[i]) if (j != 0) {
			bool p1 = path[i][j];
			bool p2 = path[j][i];
			path[i][j] = false;
			path[j][i] = false;
			if (path[i].count() == 1 && path[j].count() == 1) {
				if ((path[i] & path[j]).none()) return true;
			} else if (path[i].count() >= 1 && path[j].count() >= 1) {
				return true;
			}
			path[i][j] = p1;
			path[j][i] = p2;
		}
	}

	return false;
}

int main() {
	puts(solve() ? "YES" : "NO");
}