$\color{red}{(} \color{#FF5500}{っ} \color{#FFAA00}{◔} \color{#FFFF00}{◡} \color{#AAFF00}{◔} \color{#55FF00}{)} \color{#00FF00}{っ} \color{#00FF55}{ ♥} \color{#00FFAA}{n} \color{#00FFFF}{h} \color{#00AAFF}{i} \color{#0055FF}{x}\color{#0000FF}{i} \color{#5500FF}{n} \color{#AA00FF}{h} \color{#FF00FF}{i} \color{#FF00AA}{u} \color{#FF0055}{♥} $

//trietsigai
#include<iostream>
using namespace std;
int main(){
    int N,tong=0,i=1;
    cout<<"Input N: ";
    cin>>N;
    cout<<endl;
    while (i<=N){
        if (i%2!=0){
            tong+=i;
            i++;
        }
    }
    cout<<tong;
}