public static void main ( String [ ] args ) {
  Scanner scanner = new Scanner ( System . in ) ;
  int a = scanner . nextInt ( ) ;
  int x = scanner . nextInt ( ) ;
  int y = scanner . nextInt ( ) ;
  if ( x >= a || x <= - a ) {
    System . out . println ( - 1 ) ;
    return ;
  }
  if ( y % a == 0 ) {
    System . out . println ( - 1 ) ;
    return ;
  }
  int h = ( int ) Math . ceil ( y * 1.0 / a ) ;
  if ( h % 2 == 1 && h != 1 ) {
    if ( x == 0 ) {
      System . out . println ( - 1 ) ;
    }
    else {
      int cell = h + ( h / 2 ) - 1 ;
      if ( x > 0 ) {
        cell ++ ;
      }
      System . out . println ( cell ) ;
    }
  }
  else {
    if ( x >= a / 2.0 || x <= - a / 2.0 ) {
      System . out . println ( - 1 ) ;
    }
    else {
      int cell = h + Math . max ( h / 2 - 1 , 0 ) ;
      System . out . println ( cell ) ;
    }
  }
}

public static void main ( String [ ] args ) { Scanner scanner = new Scanner ( System . in ) ; int a = scanner . nextInt ( ) ; int x = scanner . nextInt ( ) ; int y = scanner . nextInt ( ) ; if ( x >= a || x <= - a ) { System . out . println ( - 1 ) ; return ; } if ( y % a == 0 ) { System . out . println ( - 1 ) ; return ; } int h = ( int ) Math . ceil ( y * 1.0 / a ) ; if ( h % 2 == 1 && h != 1 ) { if ( x == 0 ) { System . out . println ( - 1 ) ; } else { int cell = h + ( h / 2 ) - 1 ; if ( x > 0 ) { cell ++ ; } System . out . println ( cell ) ; } } else { if ( x >= a / 2.0 || x <= - a / 2.0 ) { System . out . println ( - 1 ) ; } else { int cell = h + Math . max ( h / 2 - 1 , 0 ) ; System . out . println ( cell ) ; } } }
(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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (binary_expression left: (identifier) right: (unary_expression operand: (identifier))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal))))) (return_statement))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal))))) (return_statement))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (cast_expression type: (integral_type) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (identifier) right: (decimal_floating_point_literal)) right: (identifier))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal)))))) alternative: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal)))) right: (decimal_integer_literal)))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) consequence: (block (expression_statement (update_expression (identifier))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))) alternative: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_floating_point_literal))) right: (binary_expression left: (identifier) right: (binary_expression left: (unary_expression operand: (identifier)) right: (decimal_floating_point_literal))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal)))))) alternative: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal)) (decimal_integer_literal)))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))))))