#include <stdio.h>

int e[1000001];

int main(){
    FILE *fin, *fout;
    fin=fopen("fractii.in", "r");
    fout=fopen("fractii.out", "w");

    int i, n, j;
    long long rez;

    fscanf(fin, "%d", &n);

    for(i=2; i<=n; i++){
        e[i]=i;
    }
    for(i=2; i<=n; i++)
        if(e[i]==i)
            for(j=i; j<=n; j+=i)
                e[j]=(e[j]/i)*(i-1);
    rez=0;
    for(i=2; i<=n; i++){
        rez+=e[i];
    }
    rez*=2;
    rez++;

    fprintf(fout, "%lld\n", rez);

    fclose(fin);
    fclose(fout);

    return 0;
    }