#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
//const long nPrime = 1000000007;
//const long nPrime = 998244353;
typedef long long ll;
int main() {
    long n;
    cin >> n;
    vector<long> viCheck(n+1,0);
    long nAns = 0;
    for(long i = 1; i <= n; i++){
        if(viCheck[i] == 1){
            continue;
        }
        long nCount = 1;
        for(; i*nCount*nCount <= n; nCount++){
            viCheck[i*nCount*nCount] = 1;
        }
        nCount--;
        nAns += nCount*nCount;
    }
    cout << nAns << endl;
    return 0;
}