Js parallax mouser применить функцию к двум дивам

<script type="text/javascript">
window.onload = function () {
 
var parallaxBox = document.getElementById ( 'box' );
var c1left = document.getElementById ( 'l1' ).offsetLeft,
c1top = document.getElementById ( 'l1' ).offsetTop,
c2left = document.getElementById ( 'l2' ).offsetLeft,
c2top = document.getElementById ( 'l2' ).offsetTop,
c3left = document.getElementById ( 'l3' ).offsetLeft,
c3top = document.getElementById ( 'l3' ).offsetTop,
c4left = document.getElementById ( 'l4' ).offsetLeft,
c4top = document.getElementById ( 'l4' ).offsetTop;
 
 
parallaxBox.onmousemove = function ( event ) {
event = event || window.event;
var x = event.clientX - parallaxBox.offsetLeft,
y = event.clientY - parallaxBox.offsetTop;
 
mouseParallax ( 'l1', c1left, c1top, x, y, 30 );
mouseParallax ( 'l2', c2left, c2top, x, y, 10 );
mouseParallax ( 'l3', c3left, c3top, x, y, 5 );
mouseParallax ( 'l4', c4left, c4top, x, y, 5 );
}
 
}
 
function mouseParallax ( id, left, top, mouseX, mouseY, speed ) {
var obj = document.getElementById ( id );
var parentObj = obj.parentNode,
containerWidth = parseInt( parentObj.offsetWidth ),
containerHeight = parseInt( parentObj.offsetHeight );
obj.style.left = left - ( ( ( mouseX - ( parseInt( obj.offsetWidth ) / 2 + left ) ) / containerWidth ) * speed ) + 'px';
obj.style.top = top - ( ( ( mouseY - ( parseInt( obj.offsetHeight ) / 2 + top ) ) / containerHeight ) * speed ) + 'px';
}
 
</script>
 
<main id="box">
<div class="layer" id="l1">
<a class="hill" href="/"> </a>
</div>
<div class="layer" id="l2">
 
</div>
<div class="layer" id="l3"> 
 
</div>
<div class="layer" id="l4">
<div class="petal">&nbsp;</div> 
 
</div>
</main>
<main id="box2">
<div class="layer" id="l1">
<a class="hill" href="/"> </a>
</div>
<div class="layer" id="l2">
 
</div>
<div class="layer" id="l3"> 
 
</div>
<div class="layer" id="l4">
<div class="petal">&nbsp;</div> 
 
</div>
</main>