source_code: 
  import java.math.*;
  import java.util.*;
  import java.io.*;
  public class Main{
      static StreamTokenizer in=new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
      static BufferedReader buffer=new BufferedReader(new InputStreamReader(System.in));
      static Scanner sc=new Scanner(System.in);
      static PrintWriter out=new PrintWriter(System.out);
      //static InputReader sc=new InputReader(System.in);
      static final int inf=10000000;
      public static void main(String args[])throws Exception {
          double n,k;
          n=sc.nextDouble();
          k=sc.nextDouble();
          double ans=0;
          ans=Math.sqrt(2.25+2*(n+k))-1.5;
          System.out.printf("%.0f\n",n-ans);
      }
      static void ssort(int arr[]){
          int len=arr.length;
          for(int i=0;i<len;i++){
              int t=(int)(len*Math.random());
              int temp=arr[t];
              arr[t]=arr[i];
              arr[i]=temp;
          }
          Arrays.sort(arr);
      }
      static int getInt()throws Exception{
          in.nextToken();
          return  (int)in.nval;
      }
  }
  
  class InputReader {
      private final InputStream stream;
      private final byte[] buf = new byte[8192];
      private int curChar, snumChars;
      public InputReader(InputStream st) {
          this.stream = st;
      }
      public int read() {
          if (snumChars == -1)
              throw new InputMismatchException();
          if (curChar >= snumChars) {
              curChar = 0;
              try {
                  snumChars = stream.read(buf);
              } catch (IOException e) {
                  throw new InputMismatchException();
              }
              if (snumChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
  
      public int nextInt() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          int res = 0;
          do {
              res *= 10;
              res += c - '0';
              c = read();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
  
      public long nextLong() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          long res = 0;
          do {
              res *= 10;
              res += c - '0';
              c = read();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
  
      public int[] nextIntArray(int n) {
          int a[] = new int[n];
          for (int i = 0; i < n; i++) {
              a[i] = nextInt();
          }
          return a;
      }
  
      public String readString() {
          int c = read();
          while (isSpaceChar(c)) {
              c = read();
          }
          StringBuilder res = new StringBuilder();
          do {
              res.appendCodePoint(c);
              c = read();
          } while (!isSpaceChar(c));
          return res.toString();
      }
  
      public String nextLine() {
          int c = read();
          while (isSpaceChar(c))
              c = read();
          StringBuilder res = new StringBuilder();
          do {
              res.appendCodePoint(c);
              c = read();
          } while (!isEndOfLine(c));
          return res.toString();
      }
  
      public boolean isSpaceChar(int c) {
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
  
      private boolean isEndOfLine(int c) {
          return c == '\n' || c == '\r' || c == -1;
      }
  
  }
  /*
  
  
  
  
   */