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#include <iostream>
#include<fstream>
#include<vector>
#include<math.h>
#include <chrono> 
using namespace std::chrono; 

using namespace std;
int main()
{
    auto start = high_resolution_clock::now(); 
    long long n;
    int * v = new int[1000001];
    int * nrPrime= new int[1000001];
    int * nrPrimeIndex = new int [1000001];
    int * altVector = new int [1000001];
    int count=0;
    long long numere=0;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(long long i=2;i<=n;i+=1)
    {
        if(v[i]==0)
        {
            nrPrime[i]=1;
            nrPrimeIndex[count]=i;
            numere=numere+(i-1);
            count++;
            v[i]=1;
            for(long long j=i*i;j<=n;j+=i)
                v[j]=1;
        }
        else
        {
            int copie=i;
            int o=0;
            int k=0;
            while(copie>1)
            {
                if(copie%nrPrimeIndex[o]==0)
                while(copie%nrPrimeIndex[o]==0)
                {
                    altVector[nrPrimeIndex[o]]++;
                    copie=copie/nrPrimeIndex[o];
                }
                o++;
            }
            long long produs=1;
            for(int parcurgere=2;parcurgere<=nrPrimeIndex[o];parcurgere++)
            {
                if(altVector[parcurgere]>0)
                {
                    produs=produs*((parcurgere-1)*(pow(parcurgere,altVector[parcurgere]-1)));
                    altVector[parcurgere]=0;
                }
            }
            numere=numere+produs;
        }
    }
    numere=numere*2+1;
    g<<numere;
    f.close();
    g.close();
    auto stop = high_resolution_clock::now(); 
    auto duration = duration_cast<microseconds>(stop - start); 
    cout << "Time in seconds:"<<duration.count()/1000000. << endl; 
    return 0;
}