"use strict"
const create = () => {
    const input = require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");
    const res = {
        "list": input, "index": 0, "max": input.length,
        "hasNext": function () { return this.index < this.max },
        "next": function () { if (!this.hasNext()) { throw "ArrayIndexOutOfBoundsException"; } else { return this.list[this.index++]; } }
    };
    return res;
}
const o = create();
const next = () => o.next()
const nextInt = () => parseInt(o.next())
const nextStrArray = () => o.next().split(" ")
const nextIntArray = () => o.next().split(" ").map(el => parseInt(el))
const nextCharArray = () => o.next().split("")
const hasNext = () => o.hasNext()
const myout = (...x) => console.log(...x)
const Main = () => {
    let [x, k, d] = next().split(" ")
    let xx = BigInt(x)
    xx = xx > 0 ? xx : -1n * xx
    let kk = BigInt(k)
    let dd = BigInt(d)
    let div = xx / dd
    let ans
    if (div >= kk) {
        ans = xx - kk * dd
    } else {
        let rem = xx % dd
        let opp = rem - dd
        if (rem < -1n*opp && div % 2n != 0n) {
            ans = -1n*opp
        } else if(rem < -1n*opp && div % 2n == 0n) {
            ans = rem
        } else if(rem >= -1n*opp && div % 2n != 0n) {
            ans = -1n*opp
        } else {
            ans = rem
        }
    }
    console.log(String(ans))

}
Main()
