#include <iostream>
#include <vector>
using namespace std;
struct SieveEratos{
  vector<bool> t;
  SieveEratos(int n):t(n+1,true){
    t[0] = t[1] = false;
    for(int i = 2; n >= i; i++){
      if(t[i]){
        for(int j = i+i; n >= j; j+=i){
          t[j] = false;
        }
      }
    }
  }
  bool operator[](int x){return t[x];}
};
int main(){
    int n;cin>>n;
    SieveEratos a(1001);
    int sm = 0;
    for(int i = 0; n >= i; i++){
        if(a[i])sm+=i;
    }
    cout << sm << endl;
}