body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Noto Sans JP";
    background-color: #f9f9f9;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    color: #333;
}

.container {
    background: white;
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    width: 320px;
    text-align: center;
}

h1 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

label {
    display: block;
    text-align: left;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

input[type="number"] {
    width: 100%;
    padding: 0.5rem;
    margin-bottom: 1rem;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-size: 1rem;
}

button {
    background-color: #0078d7;
    color: white;
    border: none;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border-radius: 4px;
    cursor: pointer;
    width: 100%;
    transition: background-color 0.3s ease;
}

button:hover {
    background-color: #005ea3;
}

#result {
    margin-top: 1rem;
    font-weight: 600;
}