.btn-container {
    position: relative;
    overflow: hidden;
    width: auto;

}

.corner-btn-first {
    font-weight: 300;
    color: #0c3948;
    padding: 8px 15px;
    width: auto;
    text-align: center;
    background: white;
    overflow: hidden;
    border: 1px black solid;
}



.corner:nth-child(5) {
    position: absolute;
    background: #0c3948;
    width: 20px;
    height: 20px;
    left: -12px;
    top: -12px;
    border-radius: 20px;
    overflow: hidden;

}

.corner:nth-child(2) {
    position: absolute;
    background: #0c3948;
    width: 20px;
    height: 20px;
    right: -12px;
    top: -12px;
    border-radius: 20px;
    z-index: 2;
}
.corner:nth-child(3) {
    position: absolute;
    background: #0c3948;
    width: 20px;
    height: 20px;
    right: -12px;
    bottom: -12px;
    border-radius: 20px;
}
.corner:nth-child(4) {
    position: absolute;
    background: #0c3948;
    width: 20px;
    height: 20px;
    left: -12px;
    bottom: -12px;
    border-radius: 20px;

}

.btn-container {
    position: relative;
    overflow: hidden;
    width: auto;

}