source_code: import java.io.BufferedReader;
  import java.io.FileWriter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.io.ObjectInputStream.GetField;
  import java.security.KeyStore.Entry;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.PriorityQueue;
  import java.util.Queue;
  import java.util.Stack;
  import java.util.StringTokenizer;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import javax.swing.JLabel;
  
  public class codeforcesreturn {
  	static class edge {
  		int u;
  		int v;
  
  		public edge(int u, int v) {
  			this.u = u;
  			this.v = v;
  		}
  
  	}
  
  	static ArrayList<Integer>[] adjlist;
  	static int[][] adjmatrix;
  	static int[][] adjmatrix2;
  	static boolean[] vis;
  	static boolean[] intialvis;
  	static boolean[] vis2;
  	static int[] counter;
  	static int V, E;
  	static Stack<Integer> st;
  	static ArrayList<Integer> arrylist;
  	static boolean flag;
  	static int[] dx = new int[] { 1, -1, 0, 0 };
  	static int[] dy = new int[] { 0, 0, 1, -1 };
  	static int[] Arr;
  	static PrintWriter pw;
  	static boolean ans = true;;
  
  	public static long gcd(long u, long v) {
  		if (u == 0)
  			return v;
  		return gcd(v % u, u);
  	}
  
  	public static void bib(int u) {
  
  		vis[u] = true;
  		for (int v : adjlist[u]) {
  			if (!vis[v]) {
  				counter[v] = 1 ^ counter[u];
  				bib(v);
  			} else if (counter[v] != (1 ^ counter[u]))
  				ans = false;
  
  		}
  	}
  
  	public static void main(String[] args) throws IOException {
  		Scanner sc = new Scanner(System.in);
  		// FileWriter f = new FileWriter("C:\\Users\\Hp\\Desktop\\out.txt");
  		PrintWriter pw = new PrintWriter(System.out);
  		int n = sc.nextInt();
  		int k = sc.nextInt();
  		int sum = n;
  
  		for (long i = 0; i < 1e5; i++) {
  			if (i * (i + 1) / 2 - (n - i) == k) {
  				System.out.println(n - i);
  				break;
  			}
  		}
  	}
  
  	static class Scanner {
  		StringTokenizer st;
  		BufferedReader br;
  
  		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();
  		}
  
  	}
  
  }