# include <fstream>

using namespace std;

const int MAX_N = 1000000;
int phi[1 + MAX_N];

int main() {
    int n;
    ifstream( "fractii.in" ) >> n;

    for ( int i = 1; i <= n; i ++ )
        phi[i] = i;
    for ( int i = 2; i <= n; i ++ )
        if ( phi[i] == i )
            for ( int j = i; j <= n; j += i )
                phi[j] = phi[j] / i * ( i - 1 );

    long long s = 0;
    for ( int i = 1; i <= n; i ++ )
        s += phi[i];

    ofstream( "fractii.out" ) << s * 2 - 1;

    return 0;
}