#include<bits/stdc++.h>

#define INF 1e9
#define llINF 1e18
#define MOD 1e9+7
#define pb push_back
#define mp make_pair 
#define F first
#define S second
#define ll long long
using namespace std;
int main(){
  int n;cin>>n;
  int ans=0;
  for(int i=2;i<=n;i++){
    bool flag=true;
    for(int j=2;j<=sqrt(i);j++)
      if(i%j==0)flag=false;
    if(flag)ans+=i;
  }
  cout<<ans<<endl;
  return 0;
}