Задача 3

import java.util.Scanner;
import java.lang.Math;

public class task3 {
    static int r,a,b,s,h,last,now,i,j;
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        r=sc.nextInt();
        b=r-1;
        a=(int) Math.floor((Math.sqrt(r*r-b*b)));
        s=a*b*4;
        h=b;
        while (true){
            last=now;
            h--;
            now= (int) Math.floor((Math.sqrt(r*r-h*h)));
            if (last==now) break;
            i++;
        }
        h=b;
        for (j=0; j<i; j++){
            h--;
            s+=4*h;
        }
        if (r==2) System.out.println("4");
        else System.out.println(s);
    }

}