function Main(input) {
    const src = input.split("\n");
    const n = parseInt(src[0]);
    let ans = 0.0;
    let r = 0.0;
    for (let i = 1; i <= n; i++) {
        r = parseFloat(src[i]);
        ans = ((3 * Math.sqrt(3)) / 4) * (r ** 2);
        console.log(ans.toFixed(5).toString());
    }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));