#include <bits/stdc++.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long long F[2000100],N;
int main(){
    fin >> N;
    for(int i = 2;i<=N;i++) F[i] = i;
    for(int i = 2;i<=N;i++)
		if(F[i] == i) for(int j = i;j<=N;j+=i) F[j]/=i,F[j]*=(i-1);
	for(int i = 3;i<=N;i++) F[i]+=F[i-1];
    fout << 2*F[N]+1;
    return 0;
}