#include <iostream>
#include <stdio.h>

int e[1000001];

int main() {
    FILE *fin, *fout;
    int n, i, j;
    long long s;
    fin = fopen( "fractii.in", "r" );
    fout = fopen( "fractii.out", "w" );
    fscanf( fin, "%d", &n );
    for( i = 2;  i <= n; i++ ) {
        e[i] = i;
    }
    for( i = 2; i <= n; i++ ) {
        if( e[i] == i ) {
            for( j = i; j <= n; j += i ) {
                e[j] = e[j] / i * (i - 1);
            }
        }
    }
    s = 0;
    for( i = 1; i <= n; i++ ) {
        s += e[i];
    }
    fprintf( fout, "%lld", s * 2 + 1 );
    fclose( fin );
    fclose( fout );
    return 0;
}