How to generate 5 different random numbers?

I have tried to generate 5 different random numbers in the for loop to generate the 5 images, but the 5 random numbers are generated exactly the same! var numberOfFaces = 5;

var theLeftSide = document.getElementById("leftSide");

for (var i = 0; i < numberOfFaces; i++) {

    //create image

    var img = document.createElement('img');

    img.src = "http://ift.tt/1GzZEsa";

    var random1 = Math.floor(Math.random() * 500 - (100 * i));

    var random2 = Math.floor(Math.random() * 500 - 100 * i);

    img.style.top = random1;

    img.style.left = random2;

    document.body.appendChild(img);

}