#include<stdio.h>

int main(void) {
	int N, sum = 0,check;
	scanf("%d", &N);
	for (int i = 2; i <= N; i++) {
		check = 1;
		for (int j = 2; j < i; j++) {
			if (i%j == 0) {
				check = 0;
				break;
			}
		}
		if (check) {
			sum += i;
		}
	}
	printf("%d", sum);
}