#include <fstream>
#include <stdlib.h>
using namespace std;

int main()
{
    int n;
    long long S=1;
    int *fi=(int *)malloc(1000001*sizeof(int));
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    for(int i=1;i<=n;++i)
        fi[i]=i;
    for(int i=2;i<=n;++i)
        if(fi[i]==i)
            for(int j=i;j<=n;j+=i)
                fi[j]-=fi[j]/i;
    for(int i=2;i<=n;++i)
        S+=2*fi[i];
    g<<S;
    return 0;
}