C :

#include<stdio.h>
int main()
{
	int VUL,D;
	while(scanf("%d%d",&VUL,&D)!=EOF)
	{
		int i=1,t=0,s=0,count=0;
		while(1)
		{
			s+=i*D;
			count+=i;
			if(s==VUL)
			{
				t=count+i-1;
				break;
			}
			if((s+(i+1)*D)>VUL)
			{
				int d;
				d=(VUL-s)%D?((VUL-s)/D+1):(VUL-s)/D;
				t=count+i+d;
				break;
			}
			else i++;
		}
		printf("%d\n",t);
	}
	return 0;
}

Java :

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		while(in.hasNext()){
			int vul = in.nextInt();
			int d = in.nextInt();
			int[] arr = new int[200];
			arr[0] = d;
			for(int i=1;i<arr.length;i++){
				int tem =(i+1)*d;  
				arr[i] = arr[i-1]+tem;
				if(vul<=arr[i]){
					if(d==arr[i])System.out.println(i+1+(vul+d-1)/d);
					else System.out.println(i+(vul+d-1)/d);
					break;
				}
			}
		}
	}

}