#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vvvvll = vector<vvvll>;
using vvvvvll = vector<vvvvll>;
#define all(A) A.begin(),A.end()
#define rep(i, n) for (ll i = 0; i < (ll) (n); i++)
template<class T>
bool chmax(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p < q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

template<class T>
bool chmin(T& p, T q, bool C = 1) {
    if (C == 0 && p == q) {
        return 1;
    }
    if (p > q) {
        p = q;
        return 1;
    }
    else {
        return 0;
    }
}

ll gcd(ll(a), ll(b)) {
    if (a == 0)return b;
    if (b == 0)return a;
    ll c = a;
    while (a % b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return b;
}
ll sqrtz(ll N) {
    ll L = max(0ll, ll(sqrt(N) - 20));
    ll R = sqrt(N) + 20;
    while (abs(R - L) > 1) {
        ll mid = (R + L) / 2;
        if (mid * mid <= N)L = mid;
        else R = mid;
    }
    return L;

}

ll inva(ll N, ll M) {
    ll mod = M;
    ll a = N, b = mod, c = 1, d = 0;
    while (b > 0) {
        ll t = a / b;
        a -= t * b;
        swap(a, b);
        c -= t * d;
        swap(c, d);
    }
    c %= mod;
    if (c < 0)c += mod;
    return c;

}

const ll mod = 998244353;
ll modPow(long long a, long long n, long long p = mod) {
    if (n == 0) return 1; // 0乗にも対応する場合
    if (n == 1) return a % p;
    if (n % 2 == 1) return (a * modPow(a, n - 1, p)) % p;
    long long t = modPow(a, n / 2, p);
    return (t * t) % p;
}

using mint = modint998244353;
mint sum(mint a, mint d, ll n) {
    if (n < 0)return 0;
    return (a + (n - 1) * d) / 2 * mint(n);
}

int main() {

    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    ll H, W, N, K;
    cin >> H >> W >> N >> K;
    if (H > W)swap(H, W);
    mint an = 0;
    mint al = (H - K + 1) * (W - K + 1);
    mint alp = al.pow(N);
    if (W < 2 * K) {
        vvll P(H, vll(W));

        rep(h, H)rep(w, W) {
            P[h][w] = (min(h, H - K) - max(0ll, h - K + 1) + 1) * (min(w, W - K) - max(0ll, w - K + 1) + 1);
            an += alp - mint(al - P[h][w]).pow(N);
        }
        an /= alp;
        cout << an.val() << endl;
        return 0;
    }
    else if (H < 2 * K) {
        mint ZH = mint(H - (K - 1) * 2);
        mint ZW = mint(W - (K - 1) * 2);
        rep(h, H) {
            ll ah = (min(h, H - K) - max(0ll, h - K + 1) + 1);
            for (ll w = 1; w <= K - 1; w++) {
                an += 2 * (alp - (mint(al - ah * w).pow(N)));
            }
            an += ZW * (alp - (mint(al - ah * K).pow(N)));
        }
        an /= alp;
        cout << an.val() << endl;
        return 0;
    }
    else {
        mint ZH = mint(H - (K - 1) * 2);
        mint ZW = mint(W - (K - 1) * 2);
        for (ll h = 1; h <= K - 1; h++)for (ll w = 1; w <= K - 1; w++) {
            an += 4 * (alp - (mint(al - h * w).pow(N)));

        }
        an += ZH * ZW * (alp - (mint(al - K * K).pow(N)));

        for (ll h = 1; h <= K - 1; h++) {
            an += 2 * ZW * (alp - (mint(al - h * K).pow(N)));
        }
        for (ll w = 1; w <= K - 1; w++) {
            an += 2 * ZH * (alp - (mint(al - w * K).pow(N)));
        }
        an /= alp;
        cout << an.val() << endl;
        return 0;
    }
}