public static void main ( String [ ] args ) throws IOException {
  Reader reader = new Reader ( ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  int n = reader . nextInt ( ) ;
  int m = reader . nextInt ( ) ;
  int k = reader . nextInt ( ) ;
  int x = 0 ;
  int lo = 1 ;
  int hi = m ;
  while ( lo <= hi ) {
    int mid = ( lo + hi ) / 2 ;
    long p = mid ;
    long sum = p ;
    long y1 = n - k ;
    long y2 = k - 1 ;
    if ( y1 > p - 1 ) {
      sum += y1 + ( p - 1 ) * p / 2 - ( p - 1 ) ;
    }
    else {
      sum += p * y1 - y1 * ( y1 + 1 ) / 2 ;
    }
    if ( y2 > p - 1 ) {
      sum += y2 + ( p - 1 ) * p / 2 - ( p - 1 ) ;
    }
    else {
      sum += p * y2 - y2 * ( y2 + 1 ) / 2 ;
    }
    if ( sum <= m ) {
      x = max ( x , mid ) ;
      lo = mid + 1 ;
    }
    else {
      hi = mid - 1 ;
    }
  }
  out . println ( x ) ;
  reader . close ( ) ;
  out . close ( ) ;
}

public static void main ( String [ ] args ) throws IOException { Reader reader = new Reader ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int n = reader . nextInt ( ) ; int m = reader . nextInt ( ) ; int k = reader . nextInt ( ) ; int x = 0 ; int lo = 1 ; int hi = m ; while ( lo <= hi ) { int mid = ( lo + hi ) / 2 ; long p = mid ; long sum = p ; long y1 = n - k ; long y2 = k - 1 ; if ( y1 > p - 1 ) { sum += y1 + ( p - 1 ) * p / 2 - ( p - 1 ) ; } else { sum += p * y1 - y1 * ( y1 + 1 ) / 2 ; } if ( y2 > p - 1 ) { sum += y2 + ( p - 1 ) * p / 2 - ( p - 1 ) ; } else { sum += p * y2 - y2 * ( y2 + 1 ) / 2 ; } if ( sum <= m ) { x = max ( x , mid ) ; lo = mid + 1 ; } else { hi = mid - 1 ; } } out . println ( x ) ; reader . close ( ) ; out . close ( ) ; }
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