#include <cstdio>

using namespace std;
int v [1000000];
int main()
{
    FILE *fin=fopen ("fractii.in","r");
    FILE *fout=fopen ("fractii.out","w");
    long long n,i,j,s;
    fscanf (fin,"%lld",&n);
    for (i=1;i<=n;i++)
        v[i]=i-1;
    for (i=2;i<=n;i++)
        for (j=2*i;j<=n;j+=i){
            v[j]-=v[i];
        }
    s=1;
    for (i=2;i<=n;i++)
        s=s+2*v[i];
    fprintf (fout,"%lld",s);
    return 0;
}