#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>

using namespace std;



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