#include <cstdio>
#include <iostream>
using namespace std;
int n;
long long sum;
int main(){
    int i,j,x;
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    sum=n;
    for(i = 2; i <= n; i++)
    {
        if(i%2==0) sum+=i/2;
        else
        sum+=i-1;
        x = n-i;
        for(j = i+i;j<=n;j+=i)
         x--;
        sum+=x;
    }
    printf("%d\n",sum);
    return 0;
}