#include <stdio.h> #include <stdlib.h> int main() { int n, m; while (scanf("%d %d\n", &n, &m) == 2) { int pole[n]; for (int i=0; i<n; i++) { pole[i] = 0; } for (int i=0; i<m; i++) { int x, y; scanf("%d %d\n", &x, &y); pole[x-1]++; pole[y-1]++; } bool nasel = false; for (int i=0; i<n; i++) { //printf("*%d:%d* ",i,pole[i]); if (pole[i] >= 4) { nasel = true; break; } } if (nasel) printf("YES\n"); else printf("NO\n"); } return 0; }