#include <stdio.h>

using namespace std;
int a[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=1;i<=n;i++)
        a[i]=i-1;
    s=1;
    for(i=2;i<=n;i++)
    {
        s+=a[i]*2;
        for(j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    }
    fprintf(fout,"%lld",s);
    fclose(fin);
    fclose(fout);
    return 0;
}