#include <cstdio>
int phi[1000001];
int main(){
    FILE* fin=fopen("fractii.in","r");
    FILE* fout=fopen("fractii.out","w");
    int n,i,j;
    long long nr=0;
    fscanf (fin,"%d",&n);
    phi[1]=1;
    for (i=2;i<=n;i++)
        phi[i]=i-1;
    for (i=2;i<=n;i++)
        for (j=2*i;j<=n;j+=i)
            phi[j]=phi[j]-phi[i];
    for (i=1;i<=n;i++)
        nr=nr+2*phi[i];
    fprintf (fout,"%lld",nr-1);
    return 0;
}