#include <iostream>
#include <cstdio>

using namespace std;

int e[1000001];

int main()
{
    FILE *fin, *fout;
    int n,i,j;
    long long k;
    fin=fopen("fractii.in","r");
    fout=fopen("fractii.out","w");
    fscanf(fin,"%d",&n);
    for(i=1;i<=n;i++)
        e[i]=i;
    k=0;
    for(i=2;i<=n;i++){
        if(e[i]==i)
            for(j=i;j<=n;j+=i)
                e[j]=e[j]/i*(i-1);
        k=k+e[i];
    }
    k=2*k+1;
    fprintf(fout,"%lld\n",k);
    fclose(fin);
    fclose(fout);
    return 0;
}