#phoneInput .field-wrapper {
                position: relative;

                width: 100%;
            }

            #phoneInput .form-group {
                display: inline-flex;
                justify-content: space-between;
                width: 250px;
                max-width: 100%;
            }

            #phoneInput .letter {
                height: 50px;
                width: 50px;
                border-radius: 0;
                border: none;
                text-align: center;
                max-width: calc((100% / 4) - 10px);

                outline-style: none;
                padding: 5px 0;
                font-size: 18px;
                font-weight: bold;
                background-color: rgba(0, 0, 0, .05);
                border-radius: 10px;

            }

            @media (max-width: 480px) {
                #phoneInput .letter {
                    font-size: 16px;
                    padding: 2px 0;
                    height: 38px;
                }
            }