import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = (1 << 63)-1
# inf = (1 << 31)-1
# md = 10**9+7
md = 998244353

class Bit:
    def __init__(self, op, e, n):
        self.op = op
        self.e = e
        self.n = n+1
        self.table = [e() for _ in range(self.n)]

    def update(self, i, x):
        i += 1
        while i < self.n:
            self.table[i] = self.op(self.table[i], x)
            i += i & -i

    # [0,i]
    def prod(self, i):
        i += 1
        res = self.e()
        while i > 0:
            res = self.op(res, self.table[i])
            i -= i & -i
        return res

h, w, n, p = LI()
xy = LLI1(n)
xy.sort()
bit = Bit(max, int, w)
for x, y in xy:
    now = bit.prod(y)+1
    bit.update(y, now)

c = bit.prod(w-1)
m = h+w-3
p = pow(p, md-2, md)
ans = 1-pow(1-p, m-c, md)*pow(1-2*p, c, md)%md
print(ans%md)