C :

#include <stdio.h>
int n, t, i;
int main(void) {
    scanf("%d", &n);
    for (i = 1; i <= n; i++) {
        if (!(i % 2)) {
            t += i;
        }
    }
    printf("%d\n", t);
    return 0;
}

C++ :

#include<iostream>

using namespace std;

int main()
{
	int n,s;
	cin>>n;
	s=0;
	for (int i=1;i<=n;i++)
	{
		if (i%2==0)
		s=s+i;
	}
	cout<<s<<endl;
	return 0;
}

Pascal :

var a,b,c:longint;
begin
  readln(a);
  c:=0;
  for b:=1 to a do
      if b mod 2=0 then c:=c+b;
  writeln(c);
end.

Python :

# coding=utf-8
n = int(input())
t = 0
for i in range(1, n + 1) :
    if not (i % 2) :
        t = t + i
print(t)