"use strict";
function Main(input) {
    const PockeyLength = Number(input.split(" ")[0]);
    const BiteLength = Number(input.split(" ")[1]);
    let ans;
    if (PockeyLength <= BiteLength * 2) {
        ans = 0;
    }
    else if (PockeyLength % BiteLength === 1) {
        ans = (Math.floor(PockeyLength / BiteLength) - 1) * BiteLength / 2;
    }
    else {
        ans = Math.floor(PockeyLength / BiteLength) * BiteLength / 2;
    }
    console.log(ans);
}
//テストの入力を受け取る
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
//Main("90 20");
//# sourceMappingURL=index.js.map