Fn.java

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package basic;
 
import java.util.Scanner;
 
/**
 *
 * @author cteam043
 */
public class Fn {
 
    public static void main(String[] args) {
 
        Scanner in = new Scanner(System.in);
        int points, lines, n1, n2;
        int [] nodes = new int [10005];
 
        while(in.hasNextInt()){
            points = in.nextInt();
            lines = in.nextInt();
 
            for(int p = 0; p < nodes.length; p++)
                nodes[p] = 0;
 
            for(int i = 0; i < lines; i++){
                n1 = in.nextInt();
                n2 = in.nextInt();
                nodes[n1]++;
                nodes[n2]++;
            }
            for(int p = 0; p < nodes.length; p++){
                if(nodes[p] >= 4){
                    System.out.println("YES");
                    return;
                }
            }
            System.out.println("NO");
        }
    }
 
}