#include <bits/stdc++.h>
using namespace std;
using LL = long long int;
#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define inc(i, n)  incID(i, 0, n)
#define dec(i, n)  decID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define dec1(i, n) decII(i, 1, n)
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))
#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define MT make_tuple
#define FI first
#define SE second
#define FR front()
#define BA back()
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
auto setmin   = [](auto & a, auto b) { return (b <  a ? a = b, true : false); };
auto setmax   = [](auto & a, auto b) { return (b >  a ? a = b, true : false); };
auto setmineq = [](auto & a, auto b) { return (b <= a ? a = b, true : false); };
auto setmaxeq = [](auto & a, auto b) { return (b >= a ? a = b, true : false); };
#define SI(v) static_cast<int>(v.size())
#define RF(e, v) for(auto & e: v)
#define until(e) while(! (e))
#define if_not(e) if(! (e))
#define ef else if
#define UR assert(false)
// 以下、入出力関係のテンプレ案のテスト
auto * IS = & cin;
// input elements (as a tuple)
template<typename U, int I> void in_(U & t) { }
template<typename U, int I, typename A, typename ... B> void in_(U & t) { (* IS) >> get<I>(t); in_<U, I + 1, B ...>(t); }
template<typename ... T> auto in() { tuple<T ...> t; in_<tuple<T ...>, 0, T ...>(t); return t; }
// input a array
template<typename T, int N> auto ain() { array<T, N> a; inc(i, N) { (* IS) >> a[i]; } return a; }
// input a (multi-dimensional) vector
template<typename T> T vin() { return * istream_iterator<T>(* IS); }
template<typename T, typename N, typename ... M> auto vin(N n, M ... m) {
	vector<decltype(vin<T, M ...>(m ...))> v(n); inc(i, n) { v[i] = vin<T, M ...>(m ...); } return v;
}
// input multi-column (as a tuple of vector)
template<typename U, int I> void colin_(U & t) { }
template<typename U, int I, typename A, typename ... B> void colin_(U & t) {
	get<I>(t).emplace_back(* istream_iterator<A>(* IS)); colin_<U, I + 1, B ...>(t);
}
template<typename ... T> auto colin(int n) {
	tuple<vector<T> ...> t; inc(i, n) { colin_<tuple<vector<T> ...>, 0, T ...>(t); } return t;
}
auto * OS = & cout;
string SP = " ", LN = "\n";
// output elements
void out() { (* OS) << LN << flush; }
template<typename A                > void out(A && a            ) { (* OS) << a      ; out(     ); }
template<typename A, typename ... B> void out(A && a, B && ... b) { (* OS) << a << SP; out(b ...); }
// output a (multi-dimensional) vector
template<typename T> ostream & operator<<(ostream & os, vector<T> const & v) {
	inc(i, v.size()) { os << (i == 0 ? "" : SP) << v[i]; } return os << flush;
}
template<typename T> void vout_(T && v) { (* OS) << v; }
template<typename T, typename A, typename ... B> void vout_(T && v, A a, B ... b) {
	for(auto && w: v) { vout_(w, b ...); (* OS) << a; }
}
template<typename T, typename ... A> void vout(T && v, A ... a) { vout_(v, a ...); out(); }

// ---- ----

auto fl = [](auto a, auto b) { assert(b != 0); return a / b - (a % b != 0 && ((a >= 0) != (b >= 0)) ? 1 : 0); };
auto ce = [](auto a, auto b) { assert(b != 0); return a / b + (a % b != 0 && ((a >= 0) == (b >= 0)) ? 1 : 0); };
auto mo = [](auto a, auto b) { assert(b != 0); a %= b; if(a < 0) { a += abs(b); } return a; };

int main() {
	auto [x, k, d] = ain<LL, 3>();
	x = abs(x);
	if(x / d >= k) { out(x - k * d); exit(0); }
	
	LL t = ce(x, d);
	if(t % 2 != k % 2) { t--; }
	out(abs(x - t * d));
}


Measured memory_bytes: 3636