public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int current = 1 ;
  int ans = 0 ;
  int n = sc . nextInt ( ) ;
  int x = sc . nextInt ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int a = sc . nextInt ( ) ;
    int b = sc . nextInt ( ) ;
    while ( current + x <= a ) {
      current = current + x ;
    }
    ans = ans + b - current + 1 ;
    current = b + 1 ;
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int current = 1 ; int ans = 0 ; int n = sc . nextInt ( ) ; int x = sc . nextInt ( ) ; for ( int i = 0 ; i < n ; i ++ ) { int a = sc . nextInt ( ) ; int b = sc . nextInt ( ) ; while ( current + x <= a ) { current = current + x ; } ans = ans + b - current + 1 ; current = b + 1 ; } 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: (decimal_integer_literal))) (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: (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)))) (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 (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)))) (while_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (identifier))) body: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier)))))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (identifier)) right: (decimal_integer_literal)))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))