#include <stdio.h>

int v[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=2;i<=n;i++)
        v[i]=i;
    for (i=2;i<=n;i++)
        if (v[i]==i)
            for (j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
    s=0;
    for (i=2;i<=n;i++)
        s=s+v[i];
    fprintf(fout,"%lld", s*2+1);
    return 0;
}