#include #include #include #include #include using namespace std; using i32 = int; using u32 = unsigned int; using i64 = long long; using u64 = unsigned long long; #define rep(i,n) for(int i=0; i<(int)(n); i++) const i64 INF = 1001001001001001001; using Modint = atcoder::static_modint<998244353>; int main(){ i64 H, W, N, K; cin >> H >> W >> N >> K; i64 f = (H-K+1) * (W-K+1); Modint p = (Modint(f)).inv().pow(N); Modint ans = 0; i64 cnt = 0; for(i64 x=1; x= 2*K-2){ for(int y=1; y= 2*K-2){ for(int x=1; x= 2*K-2 && H >= 2*K-2){ ans += Modint(f-K*K).pow(N) * (H-(2*K-2)) * (W-(2*K-2)), cnt += (H-(2*K-2)) * (W-(2*K-2)); } ans *= p; ans = Modint(H*W) - ans; cout << ans.val() << endl; return 0; } struct ios_do_not_sync{ ios_do_not_sync(){ ios::sync_with_stdio(false); cin.tie(nullptr); } } ios_do_not_sync_instance;