#807. Sum of primes
You get n. Find the sum of all prime numbers not greater than n. Write an `is_prime(x)` function.
### Input
One integer n (1 ≤ n ≤ 20000).
### Output
A number.
Examples
Input
10527
Output
6321099
Input
2824
Output
535671
💡 You can solve it with Python, JavaScript or blocks. Read the input line by line with input(). Don't print a question (like input("Number: ")). Print exactly what the output asks for, nothing more.