import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    n = int(input())
    p = [False, False] + [True] * (n-1)
    for i in range(2, n+1):
        if p[i]:
            for j in range(2*i, n+1, i):
                p[j] = False

    print(sum(i for i in range(2, n+1) if p[i]))


if __name__ == '__main__':
    main()