#include <bits/stdc++.h>

using namespace std;
#define INF 1000007
ifstream in("fractii.in");
ofstream out("fractii.out");
long long lg[INF];
int main()
{    long long n,i,j,ans=0;
     in>>n;
    for(i=1;i<=n;i++)lg[i]=i;
     for(i=2;i<=n;i++)
     {if(lg[i]==i)for(j=i;j<=n;j=j+i)lg[j]=lg[j]*(((double)i-1)/i);}
    for(i=1;i<=n;i++)ans=ans+(lg[i])*2;
    out<<ans-1;
    return 0;
}