$(document).ready(function(){
	setHillsPositions();
});

$(window).resize(function() {
	setHillsPositions();
});

function setHillsPositions(){
	var hillWidth = ($(window).width()-1020)/2;
	hillWidth = Math.round(hillWidth);
	$('div#left-box').css('width', hillWidth+'px' );
	$('div#right-box').css('width', hillWidth+'px' );
}