#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

int op(int x, int y) { return max(x, y); }
int e() { return 0; }

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, n, p;
  cin >> h >> w >> n >> p;
  vector<P> d(n);
  for(auto& [x, y]: d) cin >> x >> y, x--, y--;
  segtree<int, op, e> seg(w);
  sort(all(d));
  for(auto [_, y]: d) {
    seg.set(y, seg.prod(0, y + 1) + 1);
  }
  int cnt = seg.all_prod();
  mint p1 = mint(1) / p, p2 = p1 * 2;
  mint ans = 1 - ((1 - p1).pow(h + w - 3 - cnt) * (1 - p2).pow(cnt));
  cout << ans.val() << '\n';
}