#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream f("melc.in");
ofstream g("melc.out");
int n, i=0, s=0, dir=-1, dist=0;
f >> n;
while (s<n)
{
++i;
dir*=-1; dist+=1*dir; s+=1; if (s==n) {break;}
dir*=-1; dist+=i*dir; s+=i; if (s==n) {break;}
dir*=-1; dist+=i*dir; s+=i; if (s==n) {break;}
}
if (dist<0) dist*=-1;
g << dist;
return 0;
}