#include<iostream.h>
#include<fstream.h>
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
void fractii(long long n){
 long long i,s=0;
 for(i=2;i<=n/2;i++)
 s=s+((n/i)-1)*(i+1);
 s=s+n-1;
 s=s-(n/2)+1;
 fout<<n*n-s<<endl;
}
int main(){
long long n;
fin>>n;
fractii(n);
return 0;
}