#include <bits/stdc++.h>
std::ifstream in("fractii.in");
std::ofstream out("fractii.out");
using namespace std;
int n ;
int v[1000001];
void Input()
{
    in >> n ;
}
void euler()
{
    for(int i =1; i<=n;++i)
         v[i]=i-1;
    for(int i =2 ; i <= n ;++i)
         for(int j = 2 *i ; j<=n ;j+=i)
               v[j]-=v[i];
}
long long calc()
{long long s=0;
for(int i =2 ;i<=n;++i)
    s+=v[i];
return s*2+1;
}

int main()
{ Input();
euler();
out<<calc();
    return 0;
}