#include <bits/stdc++.h>
using namespace std;
#define x1 "fractii.in"
#define x2 "fractii.out"
ifstream in(x1);
ofstream out(x2);
#define NMAX 1000001
int eul[NMAX];

int main() {
    int n, i, j;
    long long ans = 0;
    in >> n;

    for( i = 1; i <= n; i++ )
        eul[i] = i;

    for( i = 2; i <= n; i++ ) {
        if( eul[i] == i )
            for( j = i; j <= n; j += i )
                eul[j] = eul[j] / i * ( i - 1 );
        ans += eul[i];
    }

    out << 2 * ans + 1;
    return 0;
}