Exclude entering non positive integers and Exit scripts under specific conditions

Hi，

I have the following script. I want to exclude all input non positive integers. When the input is not a positive integer, stop the script from executing the following code. Can someone help me? Thank you in advance!

  function highlightLayerInContainer (targetLayer) {
		var someTempPath = targetLayer.pathItems.rectangle(0, 0, 200, 200);
    someTempPath.name = "TEMP [for highlighting]";
		app.activeDocument.selection =  null;
		someTempPath.selected = true;
		app.doScript("target layer", "Test Set 2"); 
		someTempPath.remove();
  }

var dupN=prompt("Please enter the number of layers to copy:","8","Tips");

if (dupN!=null && dupN!="")  // I want to exclude all non positive integers entered, but I don't know how to write these conditions??
{
   

    for (var i=1;i<dupN;i++) {                                               
        highlightLayerInContainer(app.activeDocument.layers[0].layers[0]); 
        app.doScript("DupeLayer", "Test Set 2");
        app.activeDocument.layers[0].layers[0].name=i+1  
    }
}
else
{
    alert("Please do not press the \"Cancel\" button!!\n\nPlease rerun the script and enter the number of layers to copy!!");  

    // If the input is not a positive integer, I want to stop the script here and stop executing the following code. If I use 'Return', I will be prompted with an error ??
    
}


var doc = app.activeDocument;
var layers = doc.layers;


for (var i = doc.layers.length - 1; i > -1; i--) {

  recursiveRename(doc.layers[i]);
}

function recursiveRename(parent) {
  for (var i = 0; i < parent.layers.length; i++) {
    parent.layers[i].name = parent.layers[i].name.replace(/_复制.*$/, "");
    recursiveRename(parent.layers[i]);
  }
}