Walker121212,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script>
function nod(n) {
var i = 1,
result = 0,
k;
for (; i <= parseInt(n); i++) {
k = i % 2;
if (k) {
result += i;
}
}
alert(result);
return result;
}
</script>
</head>
<body>
<form name="form1" id="form1">
Введіть число
<input type="text" name="num1" size="20">
<br>
<input type="button" value="Обчислить" onclick="nod(document.form1.num1.value)">
<br>
</form>
</body>
</html>