"use strict"

function main(input) {
	
	const a = 2
	input  = parseInt(input, 10)
	let i = input

		if( i%a === 0 )
		{
			console.log( i )
		}
		else
		{

			console.log(i*a)
		}


}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));