#include <stdio.h>
#include <stdlib.h>
int v[1000001];
int main()
{
    FILE *fin, *fout;
    int n, i, d;
    long long rez;
    fin=fopen("fractii.in", "r");
    fscanf(fin, "%d", &n);
    fclose(fin);
    for(i=1; i<=n; i++)
      v[i]=i;
    for(i=2; i<=n; i++)
      if(v[i]==i)
        for(d=i; d<=n; d+=i)
          v[d]=v[d]/i*(i-1);
    rez=0;
    for(i=1; i<=n; i++)
      rez+=v[i];
    fout=fopen("fractii.out", "w");
    fprintf(fout, "%lld\n", 2*rez-1);
    fclose(fout);
    return 0;
}