#include <fstream>
#include <math.h>
#include <iostream>
using namespace std;

int prim(int x) {
    for(int i=2;i<=sqrt(x);i++)
        if(x%i==0)
            return 0;
    return 1;
}
int main()
{
    long long int x,nr_frac;
    int n,aux,var;
    ifstream is("fractii.in");
    ofstream os("fractii.out");

    is>>n;
    x = n*n;
    aux = floor(n/2);
    nr_frac = aux*(aux-1);
    var = 3;
    while(var<=n/2) {
        if(prim(var)) {
            aux = floor(n/var);
            nr_frac += aux*(aux-1)/2;
        }
        var +=2;
    }
    x -= nr_frac;
    x -= n-1;
    os<<x;
    is.close();
    os.close();
    return 0;
}