import java.util.Scanner;

/**
 * Created by Coder on 05.12.2014.
 */
public class Copy1131_ {
    public static void main(String[] args) {
        Scanner x = new Scanner(System.in);
        int n = x.nextInt();
        int k = x.nextInt();
        int time = 0, i = 1;
        long s = 1;
        while (s < n) {
            if (i >= k) {
                s += k;
            } else {
                s += i++;
            }
            time++;
        }
        System.out.println(time);
    }
}