body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    margin: 0;
    padding: 0;
}

.container {
    max-width: 800px;
    margin: 20px auto;
    padding: 20px;
    background-color: #fff;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    text-align: center;
}

h1 {
    margin: 0 0 20px;
}

.form-group {
    margin-bottom: 20px;
    text-align: left;
}

label {
    font-weight: bold;
    margin-bottom: 5px;
    display: inline-block;
}

input[type="number"] {
    width: calc(100% - 22px);
    padding: 10px;
    font-size: 16px;
    margin-top: 5px;
    border: 1px solid #ccc;
    border-radius: 4px;
}

.button {
    display: inline-block;
    margin: 10px;
    padding: 10px 20px;
    background-color: #007BFF;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

.button:hover {
    background-color: #0056b3;
}

.error {
    color: red;
    margin-top: 15px;
}

.result {
    margin-top: 20px;
    padding: 15px;
    background-color: #e9ecef;
    border-radius: 4px;
}

@media (max-width: 600px) {
    .container {
        width: 100%;
        padding: 10px;
    }
}

.footer {
    margin-top: 20px;
    text-align: center;
}

.popup {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(0, 0, 0, 0.8);
    color: white;
    padding: 20px;
    border-radius: 10px;
    text-align: center;
    z-index: 1000;
}

.popup .button {
    margin-top: 10px;
}