Simple palindromes.

Count the number of prime palindromes within the interval from a to b.A palindrome is a number that reads the same forwards and backwards, such as 7, 22, 121.A prime number is a number that has exactly 2 divisors.

Input Data

You are given two numbers, a and b, on a single line separated by a space. (0 ≤ a, b ≤ 10^7)

Output Data

Output a single number, which is the count of prime palindromes.

Examples