#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main(){
    int n, vector[1000001];
    long long numere = 1;
    fin >> n;
    for(int i=1;i<=n;i++)
        vector[i]=i;
    for(int i=1; i<=n; i++)
        for(int k=2*i;k<=n;k+=i)
            vector[k]-=vector[i];
    for(int i=2;i<=n;i++)
        numere+=2*vector[i];
    fout << numere;
    return 0;
}