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... Which one is the correct time complexity of the code snippet: constant, linear, quadratic, cubic, log(n), nlog(n) or NP-hard?