#include <stdio.h>
int main(){
    FILE *fin, *fout;
    long long n, i, j, s, a;
    fin=fopen("fractii.in", "r");
    fscanf(fin, "%lld", &n);
    fclose(fin);
    long long e[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);
    s=0;
    for(a=2; a<=n; a++)
        s+=e[a];
    fout=fopen("fractii.out", "w");
    fprintf(fout, "%lld", 2*s+1);
    fclose(fout);
    return 0;
}