#include <fstream>

using namespace std;

ifstream inFile("fractii.in");
ofstream outFile("fractii.out");

int phi[1000005];

int main()
{
    int n;
    inFile >> n;

    for(int i = 1; i <= n; i++){
        phi[i] = i-1;
    }

    for(int i = 2; i <= n/2; i++){
        for(int j = i+i; j <= n; j+=i) phi[j]-=phi[i];
    }

    long long ct = 1;
    for(int i = 2; i <= n; i++){
        ct+=2*phi[i];
    }

    outFile << ct;
}