Mirron_numbers

var prime:array[1..10000] of boolean;
    i, j, l, r, answer, reversed:longint;

//Цифра в символ
function getChar(number:longint):char;
begin
  getChar := chr(number+ord('0'));
end;

//Символ в цифру
function getInt(ch:char):longint;
begin
  getInt := ord(ch)-ord('0');
end;

//Строка в обратную ('abcd' -> 'dcba')
function reverse(str:string):string;
var reverse_str:string;
    i:longint;
begin
  reverse_str := '';
  for i := 1 to length(str) do
    reverse_str := str[i] + reverse_str;
  reverse := reverse_str;
end;

//Число в строку
function getString(number:longint):string;
var str:string;
begin
  str := '';
  while (number > 0) do begin
    str := getChar(number mod 10) + str;
    number := number div 10;
  end;
  getString := str;
end;

//Строка в число
function getNumber(str:string):longint;
var i, number:longint;
begin
  number := 0;
  for i := 1 to length(str) do
    number := number*10 + getInt(str[i]);
  getNumber := number;
end;

//Обратное к данному число
function reverseNumber(number:longint):longint;
begin
  reverseNumber := getNumber( reverse( getString( number ) ) );
end;

begin
  read(l, r);

  //Решето Эратосфена
  for i := 2 to 10000 do prime[i] := true;
  for i := 2 to 10000 do
    if prime[i] then
      for j := 2 to 10000 div i do
        prime[i*j] := false;

  //Проверка на "зеркальность"
  for i := l to r do begin
    reversed := reverseNumber(i);
    if (prime[i]) and (prime[reversed]) then
          answer := answer + 1;
  end;

  writeln(answer);
end.