#include <iostream>#include <fstream>using namespace std;ifstream in ("restmare.in");ofstream out ("restmare.out");long long int n,pana_unde,suma;int main(){ in >> n; if(n>2) {
if(n%2==1) { pana_unde = n/2; suma = (pana_unde*(pana_unde+1))/2 + ((pana_unde-1)*pana_unde)/2; } else { pana_unde = n/2-1; suma = pana_unde*(pana_unde+1); } } out << suma; return 0;}