#include <cstdio>
#include <math.h>

using namespace std;

long int v[1000005];

int main(){
    long long int s,n,i,j,h;
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    scanf("%lld",&n);
    s = 1;
    for(i = 1;i <= n;++i){
        v[i] = i-1;
    }
    for(i = 2;i <= n;++i){
        s = s + 2*v[i];
        h = n/i;
        for(j = 2;j <= h;++j){
            v[i*j] = v[i*j] - v[i];
        }
    }
    printf("%lld\n",s);
    return 0;
}