source_code: import java.io.*; 
  import java.util.*; 
  
  
  public class b{
  	
  	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; 
  		} 
  	}
  
  	public static void main(String[] args) 
  	{ 
          FastReader sc = new FastReader(); 
          //PrintWriter out = new PrintWriter(System.out); 
          double n = (double)sc.nextLong();
          double k = (double)sc.nextLong();
          
          double div = 9+8*n+8*k;
          double ss = Math.sqrt(div);
          //System.out.println(ss);
  
          ss =  (ss-3)/2;
          System.out.println( (int)(n-ss) );
  	}
  }
  