var c = 1;

function show( id ) {

	//hide old image and deselect number
	document.getElementById( 'img' + c ).className = 'hidden';
	document.getElementById( 'cir' + c ).className = 'circle-white';

	//show new image and select number
	document.getElementById( 'img' + id ).className = '';
	document.getElementById( 'cir' + id ).className = 'circle-red';
	
	//change caption
	document.getElementById( 'caption' ).innerHTML = document.getElementById( 'cap' + id ).innerHTML;
	
	c = id;

}