#include <stdio.h>

#define MAXNUM 1000000

int ciur[MAXNUM+1];

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