#include <stdio.h>

int main(void) {
	int n;	
	int sum = 0, k = 0;
	int prime_number[10000];


	scanf("%d", &n);

	if (n != 1) {

		for (int i = 2; i <= n; i++) {			
			for (int j = 2; j <= i; j++) {	
				if (j == i) {		
					prime_number[k] = j;
					k++;
				}
				if (i%j == 0) {		
					break;
				}
			}
		}

		for (int i = 0; i < k; i++) {
			sum += prime_number[i];
		}

	}
	printf("%d\n",sum);
}