public static void main ( String [ ] args ) {
  try {
    FastScanner in = new FastScanner ( ) ;
    PrintWriter out = new PrintWriter ( System . out ) ;
    int n = in . nextInt ( ) ;
    int a = in . nextInt ( ) ;
    if ( a % 2 != 0 ) {
      System . out . println ( ( a + 1 ) / 2 ) ;
    }
    else {
      int ct = a / 2 ;
      if ( n % 2 != 0 ) n -- ;
      System . out . println ( ( n / 2 ) - ct + 1 ) ;
    }
    out . flush ( ) ;
    out . close ( ) ;
  }
  catch ( Exception e ) {
    return ;
  }
}

public static void main ( String [ ] args ) { try { FastScanner in = new FastScanner ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int n = in . nextInt ( ) ; int a = in . nextInt ( ) ; if ( a % 2 != 0 ) { System . out . println ( ( a + 1 ) / 2 ) ; } else { int ct = a / 2 ; if ( n % 2 != 0 ) n -- ; System . out . println ( ( n / 2 ) - ct + 1 ) ; } out . flush ( ) ; out . close ( ) ; } catch ( Exception e ) { return ; } }
(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 (try_statement body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list)))) (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)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)))))) alternative: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (expression_statement (update_expression (identifier)))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (identifier)) right: (decimal_integer_literal))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (catch_clause (catch_formal_parameter (catch_type (type_identifier)) name: (identifier)) body: (block (return_statement))))))