// Problem: No.2230 Good Omen of White LotusNo.2230 白莲花吉兆 // Contest: yukicoder // URL: https://yukicoder.me/problems/no/2230 // Memory Limit: 512 MB // Time Limit: 2000 ms #include #define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0); #define dbg(x) cout << #x << " = " << (x) << "\n"; #define popcount(x) __builtin_popcountll((x)) #define all(v) (v).begin(), (v).end() #define pb emplace_back #define x first #define y second using namespace std; typedef long long ll; typedef pair pll; const int inf = 0x3f3f3f3f; const int mod = 998244353; struct mint { ll x; // typedef long long ll; mint(ll x = 0) : x((x % mod + mod) % mod) {} mint operator-() const { return mint(-x); } mint& operator+=(const mint a) { if ((x += a.x) >= mod) x -= mod; return *this; } mint& operator-=(const mint a) { if ((x += mod - a.x) >= mod) x -= mod; return *this; } mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this; } mint operator+(const mint a) const { mint res(*this); return res += a; } mint operator-(const mint a) const { mint res(*this); return res -= a; } mint operator*(const mint a) const { mint res(*this); return res *= a; } mint pow(ll t) const { if (!t) return 1; mint a = pow(t >> 1); a *= a; if (t & 1) a *= *this; return a; } // for prime mod mint inv() const { return pow(mod - 2); } mint& operator/=(const mint a) { return (*this) *= a.inv(); } mint operator/(const mint a) const { mint res(*this); return res /= a; } }; istream& operator>>(istream& is, mint& a) { return is >> a.x; } ostream& operator<<(ostream& os, const mint& a) { return os << a.x; } int h, w, n, p; void solve() { cin >> h >> w >> n >> p; vector vx, vy; set vis; for (int i = 1; i <= n; i++) { int x, y; cin >> x >> y; vis.insert({x, y}); vx.pb(x), vx.pb(x - 1), vx.pb(x + 1); vy.pb(y), vy.pb(y - 1), vy.pb(y + 1); } sort(all(vx)); vx.erase(unique(all(vx)), vx.end()); sort(all(vy)); vy.erase(unique(all(vy)), vy.end()); int nn = vx.size(), mm = vy.size(); auto dp = vector>(nn, vector(mm)); for (int i = 0; i < nn; i++) { for (int j = 0; j < mm; j++) { if (i) dp[i][j] = max(dp[i - 1][j], dp[i][j]); if (j) dp[i][j] = max(dp[i][j - 1], dp[i][j]); if (vis.count({vx[i], vy[j]})) dp[i][j]++; } } mint sum(h + w - 3); mint cnt(dp[nn - 1][mm - 1]); mint ans = mint(1) - mint(2) * mint(p).inv(); ans = ans.pow(cnt.x); ans = ans * (mint(1) - mint(p).inv()).pow((sum - cnt).x); cout << mint(1) - ans << "\n"; } int main() { fastio; int t = 1; // cin >> t; while (t--) { solve(); } return 0; }