#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#include<iostream>
#include<string>
#include<vector>
#include<utility>
#include<cmath>
#include<map>
#include<functional>
#include<queue>
#include<set>
#include<stack>
#include<iomanip>
#include<algorithm>
#include<unordered_map>
#include <numeric>
#include<string_view>
using namespace std;
using ll = long long;
#define rep(i,n) for(ll i=0;i<(n);i++)
#define all(i) i.begin(),i.end()
template<typename T =ll> using v = vector<T>;
template<typename T =ll> using vv = v<v<T>>;
template<typename T =ll,typename U =ll> using p = pair<T,U>;
template<typename T> T chmin(T &a,T b) {return a=min(a,b);}
template<typename T> T chmax(T &a,T b) {return a=max(a,b);}
const ll INF = (ll)1e9;
template <int MOD>
struct ModInt {
    using lint = long long;
    int val;

    // constructor
    ModInt(lint v = 0) : val(v % MOD) {
        if (val < 0) val += MOD;
    };

    // unary operator
    ModInt operator+() const { return ModInt(val); }
    ModInt operator-() const { return ModInt(MOD - val); }
    ModInt inv() const { return this->pow(MOD - 2); }

    // arithmetic
    ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
    ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
    ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
    ModInt operator/(const ModInt& x) const { return ModInt(*this) /= x; }
    ModInt pow(lint n) const {
        auto x = ModInt(1);
        auto b = *this;
        while (n > 0) {
            if (n & 1) x *= b;
            n >>= 1;
            b *= b;
        }
        return x;
    }

    // compound assignment
    ModInt& operator+=(const ModInt& x) {
        if ((val += x.val) >= MOD) val -= MOD;
        return *this;
    }
    ModInt& operator-=(const ModInt& x) {
        if ((val -= x.val) < 0) val += MOD;
        return *this;
    }
    ModInt& operator*=(const ModInt& x) {
        val = lint(val) * x.val % MOD;
        return *this;
    }
    ModInt& operator/=(const ModInt& x) { return *this *= x.inv(); }

    // compare
    bool operator==(const ModInt& b) const { return val == b.val; }
    bool operator!=(const ModInt& b) const { return val != b.val; }

    // I/O
    friend std::istream& operator>>(std::istream& is, ModInt& x) noexcept { return is >> x.val; }
    friend std::ostream& operator<<(std::ostream& os, const ModInt& x) noexcept { return os << x.val; }
};

constexpr int MOD = 1e9 + 7;
using mint = ModInt<MOD>;
void a(){
    string s;
    cin >> s;
    ll cnt = 0;
    ll ans = 0;
    rep(i,s.size()){
        if(s[i]=='R') cnt++;
        else{
            chmax(ans,cnt);
            cnt = 0;
        }
    }
    if(s[s.size()-1]=='R') chmax(ans,cnt);
    cout << ans << endl;
}

void b(){
    ll N; cin >> N;
    auto L = v<>(N,0);
    rep(i,N) cin >> L[i];
    ll cnt = 0;
    rep(i,N){
        for(ll j=i+1;j<N;j++){
            for(ll k=j+1;k<N;k++){
                if(L[i]==L[j]||L[j]==L[k]||L[i]==L[k]) continue;
                if(L[i]+L[j]>L[k]&&L[j]+L[k]>L[i]&&L[k]+L[i]>L[j]){
                    cnt++;
                } 
            }    
        }
    }

    cout << cnt << endl;
}

void c(){
    ll X,K,D; cin >> X >> K >> D;
    
    X = abs(X);

    if(K<=X/D){
        cout << X - K*D << endl;
    }else{
        ll t = X/D;
        ll q = X%D;
        ll e = K - t;
        if(e%2){
            cout << D-q << endl;
        }else{
            cout << q << endl;
        }
    }
}

void d(){
    
}


void e(){
} 

int main(void){
    c();
    return 0;
 }

Measured memory_bytes: 3600