#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

using mint = modint998244353;

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int H,W,N,K; cin >> H >> W >> N >> K;
    if (H > W) swap(H, W);
    mint ans = mint(H) * mint(W);
    if (H < 2 * K && W < 2 * K){
        // 全部埋め込む
        vector<vector<int>> imos(H + 1, vector<int>(W + 1));
        rep(i,H-K+1)rep(j,W-K+1){
            imos[i][j]++;
            imos[i + K][j + K]++;
            imos[i + K][j]--;
            imos[i][j + K]--;
        }
        rep(i,H)rep(j,W)imos[i][j+1]+=imos[i][j];
        rep(i,H)rep(j,W)imos[i+1][j]+=imos[i][j];
        rep(i,H)rep(j,W)ans -= (mint(1) - mint(imos[i][j]) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
    }
    if (H < 2 * K && W >= 2 * K){
        vector<vector<int>> imos(H + 1, vector<int>(2 * K));
        rep(i,H-K+1)rep(j,K){
            debug(i, j);
            imos[i][j]++;
            imos[i + K][j + K]++;
            imos[i + K][j]--;
            imos[i][j + K]--;
        }
        rep(i,H)rep(j,K)imos[i][j+1]+=imos[i][j];
        rep(i,H)rep(j,K)imos[i+1][j]+=imos[i][j];
        // 両端
        rep(i,H)rep(j,K)ans -= mint(2) * (mint(1) - mint(imos[i][j]) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
        rep(i,H)ans -= mint(W - 2 * K) * (mint(1) - mint(imos[i][K - 1]) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
    }
    if (H >= 2 * K && W >= 2 * K){
        vector<vector<int>> imos(2 * K, vector<int>(2 * K));
        rep(i,K)rep(j,K){
            imos[i][j]++;
            imos[i + K][j + K]++;
            imos[i + K][j]--;
            imos[i][j + K]--;
        }
        rep(i,K)rep(j,K)imos[i][j+1]+=imos[i][j];
        rep(i,K)rep(j,K)imos[i+1][j]+=imos[i][j];
        // 四隅
        rep(i,K)rep(j,K)ans -= mint(4) * (mint(1) - mint(imos[i][j]) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
        // 棒
        rep(i,K){
            ans -= mint(2) * mint(W - 2 * K) * (mint(1) - mint((i + 1) * K) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
            ans -= mint(2) * mint(H - 2 * K) * (mint(1) - mint((i + 1) * K) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
        }
        ans -= mint(H - 2 * K) * mint(W - 2 * K) * (mint(1) - mint(K * K) / (mint(H - K + 1) * mint(W - K + 1))).pow(N);
    }
    cout << ans << endl;
}