<script>
function countEars(counts, allEars, isEven)
{
	if (counts==0)
	{
		document.write(allEars);
	}
	else
	{
		if (counts==1)
		{
			allEars+=3;
			if (isEven==1)
			{
				allEars++;
			}
		}
		else
		{
			if (isEven==0)
			{
				allEars+=3;
				isEven=1;
			}
			else
			{
				allEars+=4;
				isEven=0;
			}
		}
		countEars(counts-1, allEars, isEven);
	}
}
countEars(prompt(), 0, 0);
</script>