@media (max-width: 576px) {
    .input-group {
        flex-wrap: wrap !important;
        flex-direction: column !important;
        width: 100% !important;
    }

    .input-group-text {
        flex: 1 1 100% !important;
        width: 100% !important;
        text-align: center !important;
    }

    .form-control {
        flex: 1 1 100% !important;
        width: 100% !important;
    }
}