H,W,N,P = map(int,input().split())



class SegTree:
    #単位元と結合演算はここ変える
    #いろんな種類のsegは作れないかも
    #→changeで変えれる
    
    unit = 0
    def f(self,x,y):
        return max(x,y)

    #頂点は1-index、一番下の段は0-index(bitは1-index)
    def __init__(self,N):
        self.N = N
        self.X = [self.unit] * (N + N)
    def build(self,seq):
        for i,x in enumerate(seq,self.N):
            self.X[i] = x
        for i in range(self.N-1,0,-1):
            self.X[i] = self.f(self.X[i << 1],self.X[i << 1 | 1])
    def set(self,i,x):
        i += self.N
        self.X[i] = x
        while i > 1:
            i >>= 1
            self.X[i] = self.f(self.X[i << 1],self.X[i << 1 | 1])
    def fold(self,L,R):
        #区間[L,R)についてfold
        #0 <= L,R <= N にしなきゃダメ
        L += self.N
        R += self.N
        vL = self.unit
        vR = self.unit
        while L < R:
            if L & 1:
                vL = self.f(vL,self.X[L])
                L += 1
            if R & 1:
                R -= 1
                vR = self.f(self.X[R],vR)
            L >>= 1
            R >>= 1
        return self.f(vL,vR)
    def change(self,f,unit):
        self.f = f
        self.unit = unit

seg = SegTree(W)
l = []
for _ in range(N):
    x,y = map(int,input().split())
    l.append((x-1,y-1))
l.sort()
for x,y in l:
    t = seg.fold(0,y + 1)
    seg.set(y,t + 1)
u = seg.fold(0,W)
v = H + W - 3 - u
mod = 998244353
r = pow(P,mod - 2,mod)
tmp = pow((1-r)%mod,v,mod) * pow((1-r*2)%mod,u,mod)
print((1-tmp)%mod)
#print(u,v)