.img1{
    width: 50%;
}
.img2{
    width: 70%;
}
.img3{
    width: 100%;
}
.img4{
    width: 30%;
}

.ir-siguiente {
	display:none;
	padding:20px;
	background:rgba(20, 101, 144, 0.5);
	font-size:20px;
	color: white;
	cursor:pointer;
	position: fixed;
	bottom:20px;
	right:20px;
}

.ir-atras {
	display:none;
	padding:20px;
	background:rgba(20, 101, 144, 0.5);
	font-size:20px;
	color: white;
	cursor:pointer;
	position: fixed;
	bottom:20px;
	left:20px;
}