Each evening after the dinner the SIS's students gather together to play the game of Sport Mafia. 

For the tournament, Alya puts candies into the box, which will serve as a prize for a winner. To do that, she performs n actions. The first action performed is to put a single candy into the box. For each of the remaining moves she can choose from two options:

  * the first option, in case the box contains at least one candy, is to take exactly one candy out and eat it. This way the number of candies in the box decreased by 1; 
  * the second option is to put candies in the box. In this case, Alya will put 1 more candy, than she put in the previous time. 



Thus, if the box is empty, then it can only use the second option.

For example, one possible sequence of Alya's actions look as follows:

  * put one candy into the box; 
  * put two candies into the box; 
  * eat one candy from the box; 
  * eat one candy from the box; 
  * put three candies into the box; 
  * eat one candy from the box; 
  * put four candies into the box; 
  * eat one candy from the box; 
  * put five candies into the box; 



This way she will perform 9 actions, the number of candies at the end will be 11, while Alya will eat 4 candies in total.

You know the total number of actions n and the number of candies at the end k. You need to find the total number of sweets Alya ate. That is the number of moves of the first option. It's guaranteed, that for the given n and k the answer always exists.

Please note, that during an action of the first option, Alya takes out and eats exactly one candy.

Input

The first line contains two integers n and k (1 ≤ n ≤ 10^9; 0 ≤ k ≤ 10^9) — the total number of moves and the number of candies in the box at the end. 

It's guaranteed, that for the given n and k the answer exists.

Output

Print a single integer — the number of candies, which Alya ate. Please note, that in this problem there aren't multiple possible answers — the answer is unique for any input data. 

Examples

Input


1 1


Output


0

Input


9 11


Output


4

Input


5 0


Output


3

Input


3 2


Output


1

Note

In the first example, Alya has made one move only. According to the statement, the first move is always putting one candy in the box. Hence Alya ate 0 candies.

In the second example the possible sequence of Alya's actions looks as follows: 

  * put 1 candy, 
  * put 2 candies, 
  * eat a candy, 
  * eat a candy, 
  * put 3 candies, 
  * eat a candy, 
  * put 4 candies, 
  * eat a candy, 
  * put 5 candies. 



This way, she will make exactly n=9 actions and in the end the box will contain 1+2-1-1+3-1+4-1+5=11 candies. The answer is 4, since she ate 4 candies in total.
/*==============================================
Author      : Shadman Shariar                 ||
Email       : shadman.shariar@northsouth.edu  ||
University  : North South University (NSU)    ||
Facebook    : shadman.shahriar.007            ||
==============================================*/
import java.io.*;
import java.util.*;
//import java.math.BigInteger;
import java.text.DecimalFormat;
public class Main {
public static Main obj = new Main();
public static FastReader fr = new FastReader();
public static Scanner input = new Scanner(System.in);
public static PrintWriter pw = new PrintWriter(System.out);
public static DecimalFormat df = new DecimalFormat(".000");
public static BufferedReader br = new BufferedReader
(new InputStreamReader(System.in));
public static void main (String[] args) throws Exception {
Scanner input = new Scanner (System.in);
//BigInteger bi1 = new BigInteger("000");
//StringBuilder sb = new StringBuilder();
//StringBuffer sb2 = new StringBuffer();
//StringTokenizer str = new StringTokenizer("String","Split");
 
/** Array List, Linked List, Vector
 *  Stack, Queue, Array Deque, Priority Queue
 *  Hash Set, Linked Hash Set, Tree Set
 *  Hash Map, Linked Hash Map, Tree Map */

//-----------------CODE STARTS FROM HERE------------------//



int a = input.nextInt();

int b= input.nextInt();

int sum = 0;

int c = 1;
int e =0 ;
for (int i = 1; i<=a; i++) {
	
	
	
	if (sum>b) {
		
		sum--;
		e++;
		continue;
	}
	else {
	sum+=c;
	c++;
	}
}

System.out.println(e);



//---------------------CODE ENDS HERE---------------------//
 
        //pw.close();
        input.close();
		System.exit(0);
}
 
   public static long gcd(long a, long b) {
	   if (a == 0)
		   return b;
	   return gcd(b % a, a);
   }
 
   public static long lcm(long a, long b) {
	   return (a / gcd(a, b)) * b;
   }
 
   public static long nCr(long n, long r)
   {
       return factorial(n) / (factorial(r) *
                  factorial(n - r));
   }
 
   public static long nPr(long n, long r)
   {
    return factorial(n) / factorial(n - r);
   }
 
   public static int countsubstring(String str)
   {
    int n = str.length();
    return n * (n + 1) / 2;
   }
 
   public static boolean ispalindrome(String str)
   {
    int i = 0, j = str.length() - 1;
    while (i < j) {
        if (str.charAt(i) != str.charAt(j))
            return false;
        i++;
        j--;
    }
    return true;
   }
 
   public static boolean perfectsquare(long x)
   {
    if (x >= 0) {
        long sr = (long)(Math.sqrt(x));
        return ((sr * sr) == x);
    }
    return false;
   }
 
   public static boolean perfectcube(long N)
   {
    int cube; int c = 0;
    for (int i = 0; i <= N; i++) {
        cube = i * i * i;
        if (cube == N) {
           
            c=1; break;
        }
        else if (cube > N) {
          
           c=0 ; break ;
        }
    }
	  if (c==1)return true;
	  else return false;
   }
 
  public static int divcount(int n)
   {
       boolean hash[] = new boolean[n + 1];
       Arrays.fill(hash, true);
       for (int p = 2; p * p < n; p++)
           if (hash[p] == true)
               for (int i = p * 2; i < n; i += p)
                   hash[i] = false;
       int total = 1;
       for (int p = 2; p <= n; p++) 
       {
           if (hash[p])
           {
               int count = 0;
               if (n % p == 0) 
               {
                   while (n % p == 0) 
                   {
                       n = n / p;
                       count++;
                   }
                   total = total * (count + 1);
               }
           }
       }
       return total;
   }
   
 public static void printdiv(int n)
  {
      for (int i=1; i<=Math.sqrt(n); i++)
      {
          if (n%i==0)
          {
              if (n/i == i)
                  System.out.print(" "+ i);
    
              else
                  System.out.print(i+" " + n/i + " " );
          }
      }
  }
  
   public static boolean[] sieveOfEratosthenes(int n)
   {
    boolean prime[] = new boolean[n + 1];
    for (int i = 0; i <= n; i++)
        prime[i] = true;
 
    for (int p = 2; p * p <= n; p++)
    {
        if (prime[p] == true)
        {
            for (int i = p * p; i <= n; i += p)
                prime[i] = false;
        }
    }
    prime[1]=false;
    return prime;
   }
	
   public static int removeduplicateelements(int arr[], int n){ 
		Arrays.sort(arr);
        if (n==0 || n==1){  
            return n;  
        }  
        int[] temp = new int[n];  
        int j = 0;  
        for (int i=0; i<n-1; i++){  
            if (arr[i] != arr[i+1]){  
                temp[j++] = arr[i];  
            }  
         }  
        temp[j++] = arr[n-1];      
        for (int i=0; i<j; i++){  
            arr[i] = temp[i];  
        }  
        return j;  
    }  
	
	public static int fibon(int n) {
 
		if (n <= 1) {
 
			return n;
		}
		int[] array = new int[n + 1];
		array[0] = 0;
		array[1] = 1;
		for (int i = 2; i <= n; i++) {
			array[i] = array[i - 2] + array[i - 1];
		}
 
		return array[n];
 
	}
 
	public static long sumofdigits(long n) {
		long sum = 0;
 
		while (n != 0) {
			sum = sum + n % 10;
			n = n / 10;
		}
 
		return sum;
	}
 
	public static int reversedigits(int num) {
		int rev_num = 0;
		while (num > 0) {
			rev_num = rev_num * 10 + num % 10;
			num = num / 10;
		}
		return rev_num;
	}
 
	public static int binarysearch(int arr[], int l, int r, int x) {
 
		if (r >= l) {
			int mid = l + (r - l) / 2;
			if (arr[mid] == x)
				return mid;
			if (arr[mid] > x)
				return binarysearch(arr, l, mid - 1, x);
			return binarysearch(arr, mid + 1, r, x);
		}
		return -1;
	}
 
	public static void rangeofprimenumber(int a, int b) {
		int i, j, flag;
		for (i = a; i <= b; i++) {
			if (i == 1 || i == 0)
				continue;
			flag = 1;
			for (j = 2; j <= i / 2; ++j) {
				if (i % j == 0) {
					flag = 0;
					break;
				}
			}
			if (flag == 1)
				System.out.println(i);
		}
	}
 
	public static boolean isprime(long n) {
		if (n <= 1)
			return false;
		else if (n == 2)
			return true;
		else if (n % 2 == 0)
			return false;
		for (long i = 3; i <= Math.sqrt(n); i += 2) {
			if (n % i == 0)
				return false;
		}
		return true;
	}
 
	public static long factorial(long n) {
		return (n == 1 || n == 0) ? 1 : n * factorial(n - 1);
	}
 
	public static int[] reversearrayinrange(int arr[], int start, int end) {
		int temp;
 
		while (start < end) {
			temp = arr[start];
			arr[start] = arr[end];
			arr[end] = temp;
			start++;
			end--;
		}
	  return arr;
	}
 
    public static class FastReader {
		BufferedReader br;
		StringTokenizer st;
 
		public FastReader() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}
		String next() {
			while (st == null || !st.hasMoreElements()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}
 
		int nextInt() {
			return Integer.parseInt(next());
		}
 
		long nextLong() {
			return Long.parseLong(next());
		}
 
		double nextDouble() {
			return Double.parseDouble(next());
		}
 
		String nextLine() {
			String str = "";
			try {
				str = br.readLine();
			} catch (IOException e) {
				e.printStackTrace();
			}
			return str;
		}
	}
}