#include <stdio.h>
#include <math.h>

int p[1001];

int main(){
        int i, j;
        int N;
        int sum = 0;
        p[0] = -1;
        p[1] = -1;
        for(i = 2; i < sqrt(1001); i++){
                if(p[i] == -1) continue;
                for(j = 2; i * j < 1001; j++){
                        p[i * j] = -1;
                }
        }

        scanf("%d", &N);
        for(i = 2; i <= N; i++){
                sum += p[i] == 0 ? i : 0;
        }
        printf("%d\n", sum);
        return 0;

}