public static void main ( String [ ] args ) {
  FastScanner scan = new main ( ) . new FastScanner ( ) ;
  long a = scan . nextLong ( ) ;
  long b = scan . nextLong ( ) ;
  long ans = ( long ) ( - 3 + Math . sqrt ( 9 + 8 * ( a + b ) ) ) / 2 ;
  System . out . print ( a - ans ) ;
}

public static void main ( String [ ] args ) { FastScanner scan = new main ( ) . new FastScanner ( ) ; long a = scan . nextLong ( ) ; long b = scan . nextLong ( ) ; long ans = ( long ) ( - 3 + Math . sqrt ( 9 + 8 * ( a + b ) ) ) / 2 ; System . out . print ( a - ans ) ; }
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