#include <bits/stdc++.h>

using namespace std;
int n,a[1000005];

int main()
{
    long long i,j,s=1;
    ifstream fin("fractii.in");
    fin>>n;
    fin.close();
    for(i=2;i<=n;++i)
            a[i]=i-1;
    for(i=2;i<=n;++i)
        for(j=i+i;j<=n;j=j+i)
    {
        a[j]-=a[i];
    }
    for(i=2;i<=n;i++)
        s+=2*a[i];
    ofstream fout("fractii.out");
    fout<<s;
    fout.close();

    return 0;
}