source_code: import java.util.*;
  
  public class B
  {
  	static long sumN(long n)
  	{
  		return n * (n + 1) / 2;
  	}
  
  	static int binSearchPuts(int n, int k)
  	{
  		int L = 1;
  		int U = n;
  		int M = (L + U) / 2;
  
  		while(L <= U)
  		{
  			long left = sumN(M) - (n - M);
  			
  			if(left < k)
  			{
  				L = M + 1;
  			}
  			else if(left > k)
  			{
  				U = M;
  			}
  			else
  			{
  				break;
  			}
  
  			M = (L + U) / 2;
  		}
  
  		return M;
  	}
  
  	public static void main(String[] args)
  	{
  		Scanner input = new Scanner(System.in);
  
  		int n = input.nextInt();
  		int k = input.nextInt();
  
  		long ate = n - binSearchPuts(n, k);
  		System.out.println(ate);
  	}
  }