public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  long n = sc . nextLong ( ) ;
  long k = sc . nextLong ( ) ;
  long sum = 0 ;
  long i = 1 ;
  for ( i = 1 ;
  i <= n ;
  i ++ ) {
    sum = i * ( i + 1 ) ;
    sum = sum / 2 ;
    sum -= ( n - i ) ;
    if ( sum == k ) {
      System . out . println ( n - i ) ;
      break ;
    }
  }
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; long n = sc . nextLong ( ) ; long k = sc . nextLong ( ) ; long sum = 0 ; long i = 1 ; for ( i = 1 ; i <= n ; i ++ ) { sum = i * ( i + 1 ) ; sum = sum / 2 ; sum -= ( n - i ) ; if ( sum == k ) { System . out . println ( n - i ) ; break ; } } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (for_statement init: (assignment_expression left: (identifier) right: (decimal_integer_literal)) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal)))))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (expression_statement (assignment_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier))))) (break_statement)))))))