C++ :

#include<iostream>
using namespace std;
int main()
{
	int n,sum=0;
	cin>>n;
	for (int i=1; i<=n; i++)
		if (i%2) sum+=i;
	cout<<sum<<endl;
	return 0;
}

Pascal :

var s,n,i:longint;
begin
  readln(n);
  s:=0;
  for i:=1 to n do
    if odd(i) then s:=s+i;
  writeln(s);
end.

Java :

import java.util.Scanner;
public class Main
{	static Scanner inputScanner=new Scanner(System.in);
	public static void  main(String[] argStrings)
	{
		int Sn=0;
		int N=inputScanner.nextInt();
		for (int i = 1; i <= N; i+=2)
			Sn+=i;
		System.out.println(Sn);
	}
}