#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using mint = atcoder::modint998244353;

int op(int l, int r) { return std::max(l, r); }
int e() { return 0; }

int main() {
    int H, W, N, P;
    cin >> H >> W >> N >> P;
    vector<pair<int, int>> xy(N);
    for (auto &[x, y] : xy) cin >> x >> y, --y;
    sort(xy.begin(), xy.end());

    atcoder::segtree<int, op, e> tree(W);
    for (auto [_, y] : xy) tree.set(y, tree.prod(0, y + 1) + 1);

    const int k = tree.all_prod();
    mint p = mint(1) / P;
    cout << (1 - (1 - p).pow(H + W - 3 - k) * (1 - p * 2).pow(k)).val() << endl;
}