Евгений

@media only screen and (min-width : 768px) {
    .flex-row.row {
        display: flex;
        flex-wrap: wrap;
    }
    .flex-row.row > [class*='col-'] {
        display: flex;
        flex-direction: column;
    }
}

document.getElementsByTagName('html')[0].style.height="300px";

$(document).on("focus", "input", function() { 
    $(this).mask("(999) 999-99-99",{placeholder:"_"});
  });