public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int l = sc . nextInt ( ) ;
  int m = sc . nextInt ( ) - 1 ;
  int mas [ ] = new int [ l ] ;
  for ( int i = 0 ;
  i < l ;
  i ++ ) {
    mas [ i ] = sc . nextInt ( ) ;
  }
  int ans = 0 ;
  for ( int i = 0 ;
  i < l ;
  i ++ ) {
    if ( mas [ i ] == 1 ) {
      if ( Math . abs ( i - m ) == 0 || 2 * m - i < 0 || 2 * m - i >= l || mas [ 2 * m - i ] == 1 ) {
        ans ++ ;
      }
    }
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int l = sc . nextInt ( ) ; int m = sc . nextInt ( ) - 1 ; int mas [ ] = new int [ l ] ; for ( int i = 0 ; i < l ; i ++ ) { mas [ i ] = sc . nextInt ( ) ; } int ans = 0 ; for ( int i = 0 ; i < l ; i ++ ) { if ( mas [ i ] == 1 ) { if ( Math . abs ( i - m ) == 0 || 2 * m - i < 0 || 2 * m - i >= l || mas [ 2 * m - i ] == 1 ) { ans ++ ; } } } System . out . println ( ans ) ; }
(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: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)) right: (decimal_integer_literal)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (decimal_integer_literal))) consequence: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (binary_expression left: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier)))) right: (decimal_integer_literal)) right: (binary_expression left: (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (identifier)) right: (identifier)) right: (decimal_integer_literal))) right: (binary_expression left: (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (identifier)) right: (identifier)) right: (identifier))) right: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (binary_expression left: (decimal_integer_literal) right: (identifier)) right: (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))))))