#! usr/bin/env python
# -*- coding: utf-8 -*-


def is_prime(x):
    i = 2
    while i * i <= x:
        if x % i == 0:
            return False
        i += 1
    return True


def main():
    n = int(input())

    p = []
    for i in range(2, n+1):
        if is_prime(i):
            p.append(i)

    print(sum(p))


if __name__ == '__main__':
    main()