#include<bits/stdc++.h>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
using namespace std;
typedef long long ll;
int INF = (1LL << 30) - 1;
int MOD = 1e9+7;
main(){
    int N;
    cin >> N;
    int sum = 0;
    rep(i,2,N+1){
        int f = 1;
        rep(j,2,i){
            if(i % j == 0)f = 0;
        }
        sum += i * f;
    }
    cout << sum << endl;
}