var pictures = new Array(
	"images/zdj1.JPG",
	"images/zdj2.JPG",
	"images/zdj3.JPG",
	"images/zdj4.JPG",
	"images/zdj5.JPG"
);

function randomPic(imgId) {
	document.getElementById(imgId).src = pictures[Math.floor(Math.random() * (pictures.length))];
}