#include<bits/stdc++.h>
using namespace std;
#define ll long long 
#define pb push_back 
#define fr first
#define sc second
#define Rep(i,n) for(int i=0;i<(n);i++)
#define All(v) v.begin(),v.end()
#define Uniq(v) v.erase(unique(all(v)),v.end())
typedef pair<int, int> Pii; 
typedef pair<int, Pii> Pip;
typedef pair<string, int> Psi;
typedef vector<int> Vi;
const int INF = (1<<30);
const int dx[]={1,0,-1,0}, dy[]={0,-1,0,1};

int main()
{
  ll L;
  scanf("%lld", &L);
  printf("%lld\n", (L-1)/2 * (L-1) / 2);
  return 0;
}