#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using i32 = int;
using u32 = unsigned int;
#define rep(i,n) for(int i=0; i<(n); i++)


int main() {
    i64 N; cin >> N;
    i64 n = N/2 + 1;
    cout << (n * (n+1) / 2) << endl;
    return 0;
}



struct ios_do_not_sync{
    ios_do_not_sync(){
        std::ios::sync_with_stdio(false);
        std::cin.tie(nullptr);
    }
} ios_do_not_sync_instance;