.calculator{
	border:2px solid #ddd;
	width: 280px;
	box-sizing: border-box;
	margin: 40px auto 0;
	font-family: verdana;
}
.calculator .form-control{
	height: 60px;
}
.calculator .form-group{
	margin-bottom: 0;
}
.calculator input[type=text]{
	font-size: 1.5rem;
	color:blue;
}
.calculator .btn {
	font-size: 1.5rem;
	color:#333;
	width: 80px;
}
.calculator .btn-op {
	background-color: #999999;
}