#include <iostream>
#include <fstream>

using namespace std;

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

const int MAX=1000005;
int n,v[MAX],m,i,j,d,eul;
long long cnt;

int main()
{
    fin >> n;
    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)
            for(j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
    for(i=1;i<=n;i++)
        cnt+=1LL*v[i];
    fout << 2LL*cnt-1LL;
    return 0;
}