class Human{
	int eatLength;
	int eatedPokkey;
	
	public Human(int i){
		this.eatLength = i;
		this.eatedPokkey = 0;
	}
}

public class No_63{
	public static void main(String[] args){
		java.util.Scanner sc = new java.util.Scanner(System.in);
		int pokkey = sc.nextInt();
		int k = sc.nextInt();
		
		Human haruka = new Human(k);
		Human yuu = new Human(k);
		
		while(pokkey > 0){
			if(pokkey - (haruka.eatLength + yuu.eatLength) > 0){
				haruka.eatedPokkey += haruka.eatLength;
				yuu.eatedPokkey += yuu.eatLength;
				pokkey -= haruka.eatLength + yuu.eatLength;
			}
			else{
				haruka.eatedPokkey += pokkey;
				pokkey = 0;
			}
		}
		System.out.println(yuu.eatedPokkey);
		sc.close();
	}
}