# include <algorithm>
# include <cstdio>

int V[1000000] ;
int N ;
long long sol ;

int comp ( void ) {
    return ++sol ;
}

int main ( void ) {
    fscanf ( fopen ( "fractii.in", "r" ) , "%d", &N ) ;
    std :: generate_n ( V, N, comp ) ;
    sol = 0 ;
    for ( int i = 1; i < N; ++i ) {
        if ( V[i] == i + 1 ) {
            for ( int j = i + 1; j < N; j += i + 1 ) {
                V[j] /= i + 1, V[j] *= i ;
            }
        }
        sol += V[i] ;
    }
    fprintf ( fopen ( "fractii.out", "w" ) , "%lld", sol * 2 + 1 ) ;
}