function click_d(i) {
	for (index = 1; index <= 20; index++) {
		if (index != i) {
			document.getElementById("div" + index).style.visibility = 'hidden';
			document.getElementById("div" + index).style.display = 'none';
		}
	}
	
	if (document.getElementById("div" + i).style.visibility == 'visible' ||
		document.getElementById("div" + i).style.display == 'block') {
		
			document.getElementById("div" + i).style.visibility = 'hidden';
			document.getElementById("div" + i).style.display = 'none';	
	}
	else {
		document.getElementById("div" + i).style.visibility = 'visible';
		document.getElementById("div" + i).style.display = 'block';
	}
}