.btn-group > .btn:first-child:not(:last-child):not(.dropdown-toggle) {
    border-bottom-left-radius: 5px;
    border-top-left-radius: 5px;
}

.btn-group > .btn:last-child:not(:first-child),
.btn-group > .dropdown-toggle:not(:first-child) {
    border-bottom-right-radius: 5px;
    border-top-right-radius: 5px;
}

#example {
    width: 100% !important;
}