border-radius属性失效了Ծ‸Ծ

 .btn-circle {
        width: 30px;
        height: 30px;
        text-align: center;
        padding: 4px 0;
        font-size: 16px;
        font-weight:600;
        line-height: 1.428571429;
        border-radius: 15px !important;
    }

<input type="button" value="-" id="cut" class="btn btn-info btn-circle" />

bootstrap3.0