static int pairs ( int n ) {
  int [ ] [ ] c = new int [ 10 ] [ 10 ] ;
  int tmp = 1 ;
  for ( int i = 1 ;
  i <= n ;
  i ++ ) {
    if ( i >= tmp * 10 ) tmp *= 10 ;
    c [ i / tmp ] [ i % 10 ] ++ ;
  }
  int ans = 0 ;
  for ( int i = 1 ;
  i < 10 ;
  i ++ ) for ( int j = 1 ;
  j < 10 ;
  j ++ ) ans += c [ i ] [ j ] * c [ j ] [ i ] ;
  return ans ;
}

static int pairs ( int n ) { int [ ] [ ] c = new int [ 10 ] [ 10 ] ; int tmp = 1 ; for ( int i = 1 ; i <= n ; i ++ ) { if ( i >= tmp * 10 ) tmp *= 10 ; c [ i / tmp ] [ i % 10 ] ++ ; } int ans = 0 ; for ( int i = 1 ; i < 10 ; i ++ ) for ( int j = 1 ; j < 10 ; j ++ ) ans += c [ i ] [ j ] * c [ j ] [ i ] ; return ans ; }
(method_declaration (modifiers) type: (integral_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal)) dimensions: (dimensions_expr (decimal_integer_literal))))) (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: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (expression_statement (assignment_expression left: (identifier) right: (decimal_integer_literal)))) (expression_statement (update_expression (array_access array: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (identifier))) index: (binary_expression left: (identifier) right: (decimal_integer_literal))))))) (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: (decimal_integer_literal)) update: (update_expression (identifier)) body: (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier)) right: (array_access array: (array_access array: (identifier) index: (identifier)) index: (identifier))))))) (return_statement (identifier))))