#include <stdio.h>

using namespace std;
int e[1000002];
int main()
{
    FILE *in,*out;
    in = fopen("fractii.in","r");
    out = fopen("fractii.out","w");
    int N,i,j;
    long long S = 0;
    fscanf(in,"%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);
        }
    }
    for(i = 2;i <= N;i++)
        S = S + 2 * e[i];
    S = S + 1;
    fprintf(out,"%lld\n", S);
        return 0;
}