#include <iostream>
#include <fstream>
using namespace std;
ifstream fi("fractii.in");
ofstream fo("fractii.out");
int N;
int dp[1000001];
void DP()
{
    for(int i=2;i<=N;i++)
    {
        int con=(i-1)*2;
        int conn=0;
        for(int j=2;j*j<=i;j++)
        {
            if(i%j==0)
            {
                conn=conn+(i/j-1)*2;
                if(i/j%j!=0)
                    conn=conn+(i/(i/j)-1)*2;
            }
        }
        dp[i]=dp[i-1]+con-conn;
    }
}
int main()
{
    fi>>N;
    dp[1]=1;
    DP();
    fo<<dp[N];
    return 0;
}