/*課題3*/
th {text-align: center;
    width: 50px;
    font-family: "serif";
    font-weight: hold;}
th:first-child {background: red;}
th:first-child + th {background-color: pink;}
th:first-child + th + th {background-color: orange;}
th:first-child + th + th + th {background-color: aqua;}
th:first-child + th + th + th + th {background-color: maroon;}
th:first-child + th + th + th + th + th {background-color: yellow;}
th:first-child + th + th + th + th + th + th {background-color: blue;}

td {text-align: right;
    width: 50px;
    font-family: Georgia, serif;
    font-weight: lighter;}
td:first-child {color: red;}
td:last-child {color: blue;}
td.holiday {color: red;}