// yukicoder: No.713 素数の和
// 2019.4.14 bal4u

#include <stdio.h>
#include <string.h>

#define MAX  1000
#define SQRT 31
char prime[MAX+5];			// 1: if prime

void sieve()
{
	int i, j;

	memset(prime, 1, sizeof(prime));
	for (i = 4; i <= MAX; i+=2) prime[i] = 0;
	prime[0] = prime[1] = 0, prime[2] = 1;
	for (i = 3; i <= SQRT; i += 2) if (prime[i]) {
		for (j = i * i; j < MAX; j += i) prime[j] = 0;
	}
}

int main()
{
	int i, N, ans;

	sieve();
	scanf("%d", &N);
	ans = 0; for (i = 2; i <= N; i++) if (prime[i]) ans += i;
	printf("%d\n", ans);
	return 0;
}