#include<bits/stdc++.h>
using namespace std;
using Int = long long;

Int isprime(Int x){
  if(x<=1) return 0;
  for(Int i=2;i*i<=x;i++)
    if(x%i==0) return 0;
  return 1;
}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  Int ans=0;
  for(Int i=1;i<=n;i++) ans+=isprime(i)*i;
  cout<<ans<<endl;
  return 0;
}