#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream fin("prim.in");
ofstream fout("prim.out");
ll phi(ll n)
{
    //formula n*(1-1/p1)*(1-1/p2)*...
    ll result=n;
    for(ll i=2;i*i<=n;i++)
    {
        if(n%i==0)
        {
            while(n%i==0)
                n/=i;
            result-=result/i;
        }
    }
    if(n>1)result-=result/n;
    return result;
}
const int dim=1e6;
ll n,dp[dim];
int main()
{
    fin>>n;
    dp[1]=1;
    for(ll i=2;i<=n;i++)
        dp[i]=dp[i-1]+2*phi(i);
    fout<<dp[n];
}