#include <iostream>
#include <fstream>
#include <cstring>
#include <algorithm>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int C[1000001];
void CIUR(int N,long long &nr)
{
    for(int i=3;i<=N/2;i+=2)
    {
        int cnt=0;
        if(!C[i])
        {
            for(int j=i*2;j<=N;j+=i)
            {
                C[j]=1;
                cnt++;
            }
            nr=nr-cnt*(cnt+1);
        }
    }

}
int main()
{
    int n;
    fin>>n;

    long long nr=(long long)n*n-(n-1)-(n/2*(n/2-1));
    CIUR(n,nr);
    fout<<nr;
    return 0;
}