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

typedef long long int int64;

#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
#define ABS(a) ((a)>(0)?(a):-(a))

int isPrime(int n){
  if(n<=1) return 0;
  if(n<=3) return 1;
  if(n%2==0) return 0;
  int k=3;
  while(k*k<=n){
    if(n%k==0) return 0;
    k+=2;
  }
  return 1;
}

void run(void){
  int n;
  scanf("%d",&n);
  int sum=0;
  int i;
  for(i=1;i<=n;i++)
    if(isPrime(i))
      sum+=i;
  printf("%d\n",sum);
}

int main(void){
  run();
  return 0;
}