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.
import java.io.*;
import java.util.*;
public class l {
    ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////                                                                                                               /////////
////////                                                                                                               /////////
////////   HHHH        HHHH  EEEEEEEEEEEEE   MMMM          MMMM         OOOOOO             SSSSSSS      EEEEEEEEEEEEE  /////////
////////   HHHH        HHHH  EEEEEEEEEEEEE   MMMMMM      MMMMMM      OOO      OOO        SSSS   SSS     EEEEEEEEEEEEE  /////////
////////   HHHH        HHHH  EEEEE           MMMM MMM  MMM MMMM    OOO          OOO    SSSS       SSS   EEEEE          /////////
////////   HHHH        HHHH  EEEEE           MMMM  MMMMMM  MMMM   OOO            OOO   SSSS             EEEEE          /////////
////////   HHHH        HHHH  EEEEE           MMMM          MMMM  OOO              OOO   SSSSSSS         EEEEE          /////////
////////   HHHHHHHHHHHHHHHH  EEEEEEEEEEE     MMMM          MMMM  OOO              OOO      SSSSSS       EEEEEEEEEEE    /////////
////////   HHHHHHHHHHHHHHHH  EEEEEEEEEEE     MMMM          MMMM  OOO              OOO         SSSSSSS   EEEEEEEEEEE    /////////
////////   HHHH        HHHH  EEEEE           MMMM          MMMM   OOO            OOO              SSSS  EEEEE          /////////
////////   HHHH        HHHH  EEEEE           MMMM          MMMM    OOO          OOO     SSS       SSSS  EEEEE          /////////
////////   HHHH        HHHH  EEEEEEEEEEEEE   MMMM          MMMM      OOO      OOO        SSS    SSSS    EEEEEEEEEEEEE  /////////
////////   HHHH        HHHH  EEEEEEEEEEEEE   MMMM          MMMM         OOOOOO             SSSSSSS      EEEEEEEEEEEEE  /////////
////////                                                                                                               /////////
////////                                                                                                               /////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
    static int mod = (int) (1e9 + 7);
    // static int n;
    static StringBuilder sol;

    static class pair implements Comparable<pair> {
        int left, type;
        double w;
        public pair(int x, double y) {
            left = x;
            w = y;
            type= 0;
        }

        public int compareTo(pair o) {
            return Double.compare(w,o.w);
        }

        public String toString() {
            return left + " " + w;
        }
    }

    static class tri implements Comparable<tri> {
        int st, end,len, side;

        tri(int a, int b, int c,int d) {
            st = a;
            end = b;
            len = c;
            side=d;
        }

        public int compareTo(tri o) {
            if (st == o.st) return end - o.end;
            return st - o.st;
        }

        public String toString() {
            return st + " " + end ;
        }
    }


    static ArrayList<pair>[]adj;


    static int n;
    public static void main(String[] args) throws IOException {
        Scanner sc = new Scanner(System.in);
        //FileWriter f = new FileWriter("C:\\Users\\Ibrahim\\out.txt");
        PrintWriter pw = new PrintWriter(System.out);
        int n = sc.nextInt();
        int k = sc.nextInt();
        int lo=0;
        int hi=n;
        int ans=0;
        while (lo<=hi){
            int mid=lo+hi>>1;
            long rem= n-mid;
            rem*=(rem+1);
            rem/=2;
            rem-=mid;
            //pw.println(rem+" "+mid+" "+k);
            if (rem==k){
                ans=mid;
                break;
            }
            else if (rem>k){
                lo=mid+1;
            }
            else hi=mid-1;
        }
        pw.println(ans);
        pw.flush();
    }
    static long gcd(long a ,long b){
        if (a==0)return b;
        return gcd(b%a,a);
    }






    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(FileReader r) {
            br = new BufferedReader(r);
        }

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

        public long nextLong() throws IOException {
            return Long.parseLong(next());
        }

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public double nextDouble() throws IOException {
            String x = next();
            StringBuilder sb = new StringBuilder("0");
            double res = 0, f = 1;
            boolean dec = false, neg = false;
            int start = 0;
            if (x.charAt(0) == '-') {
                neg = true;
                start++;
            }
            for (int i = start; i < x.length(); i++)
                if (x.charAt(i) == '.') {
                    res = Long.parseLong(sb.toString());
                    sb = new StringBuilder("0");
                    dec = true;
                } else {
                    sb.append(x.charAt(i));
                    if (dec)
                        f *= 10;
                }
            res += Long.parseLong(sb.toString()) / f;
            return res * (neg ? -1 : 1);
        }

        public boolean ready() throws IOException {
            return br.ready();
        }
    }
}