// #pragma GCC target("avx")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
void chmax(T &a, const T &b) {a = (a > b? a : b);}
template<typename T>
void chmin(T &a, const T &b) {a = (a < b? a : b);}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

template<int MOD>
struct Modular_Int {
    int x;

    Modular_Int() = default;
    Modular_Int(int x_) : x(x_ >= 0? x_%MOD : (MOD-(-x_)%MOD)%MOD) {}

    int val() const {
        return (x%MOD+MOD)%MOD;
    }
    int get_mod() const {
        return MOD;
    }

    Modular_Int<MOD>& operator^=(int d)  {
        Modular_Int<MOD> ret(1);
        int nx = x;
        while(d) {
            if(d&1) ret *= nx;
            (nx *= nx) %= MOD;
            d >>= 1;
        }
        *this = ret;
        return *this;
    }
    Modular_Int<MOD> operator^(int d) const {return Modular_Int<MOD>(*this) ^= d;}
    Modular_Int<MOD> pow(int d) const {return Modular_Int<MOD>(*this) ^= d;}
    
    //use this basically
    Modular_Int<MOD> inv() const {
        return Modular_Int<MOD>(*this) ^ (MOD-2);
    }
    //only if the module number is not prime
    //Don't use. This is broken.
    // Modular_Int<MOD> inv() const {
    //     int a = (x%MOD+MOD)%MOD, b = MOD, u = 1, v = 0;
    //     while(b) {
    //         int t = a/b;
    //         a -= t*b, swap(a, b);
    //         u -= t*v, swap(u, v);
    //     }
    //     return Modular_Int<MOD>(u);
    // }

    Modular_Int<MOD>& operator+=(const Modular_Int<MOD> other) {
        if((x += other.x) >= MOD) x -= MOD;
        return *this;
    }
    Modular_Int<MOD>& operator-=(const Modular_Int<MOD> other) {
        if((x -= other.x) < 0) x += MOD;
        return *this;
    }
    Modular_Int<MOD>& operator*=(const Modular_Int<MOD> other) {
        int z = x;
        z *= other.x;
        z %= MOD;
        x = z;
        if(x < 0) x += MOD;
        return *this;
    }
    Modular_Int<MOD>& operator/=(const Modular_Int<MOD> other) {
        return *this = *this * other.inv();
    }
    Modular_Int<MOD>& operator++() {
        x++;
        if (x == MOD) x = 0;
        return *this;
    }
    Modular_Int<MOD>& operator--() {
        if (x == 0) x = MOD;
        x--;
        return *this;
    }
    
    Modular_Int<MOD> operator+(const Modular_Int<MOD> other) const {return Modular_Int<MOD>(*this) += other;}
    Modular_Int<MOD> operator-(const Modular_Int<MOD> other) const {return Modular_Int<MOD>(*this) -= other;}
    Modular_Int<MOD> operator*(const Modular_Int<MOD> other) const {return Modular_Int<MOD>(*this) *= other;}
    Modular_Int<MOD> operator/(const Modular_Int<MOD> other) const {return Modular_Int<MOD>(*this) /= other;}
    
    Modular_Int<MOD>& operator+=(const int other) {Modular_Int<MOD> other_(other); *this += other_; return *this;}
    Modular_Int<MOD>& operator-=(const int other) {Modular_Int<MOD> other_(other); *this -= other_; return *this;}
    Modular_Int<MOD>& operator*=(const int other) {Modular_Int<MOD> other_(other); *this *= other_; return *this;}
    Modular_Int<MOD>& operator/=(const int other) {Modular_Int<MOD> other_(other); *this /= other_; return *this;}
    Modular_Int<MOD> operator+(const int other) const {return Modular_Int<MOD>(*this) += other;}
    Modular_Int<MOD> operator-(const int other) const {return Modular_Int<MOD>(*this) -= other;}
    Modular_Int<MOD> operator*(const int other) const {return Modular_Int<MOD>(*this) *= other;}
    Modular_Int<MOD> operator/(const int other) const {return Modular_Int<MOD>(*this) /= other;}

    bool operator==(const Modular_Int<MOD> other) const {return (*this).val() == other.val();}
    bool operator!=(const Modular_Int<MOD> other) const {return (*this).val() != other.val();}
    bool operator==(const int other) const {return (*this).val() == other;}
    bool operator!=(const int other) const {return (*this).val() != other;}

    Modular_Int<MOD> operator-() const {return Modular_Int<MOD>(0LL)-Modular_Int<MOD>(*this);}

    //入れ子にしたい
    // friend constexpr istream& operator>>(istream& is, mint& x) noexcept {
    //     int X;
    //     is >> X;
    //     x = X;
    //     return is;
    // }
    // friend constexpr ostream& operator<<(ostream& os, mint& x) {
    //     os << x.val();
    //     return os;
    // }
};

// const int MOD_VAL = 1e9+7;
const int MOD_VAL = 998244353;
using mint = Modular_Int<MOD_VAL>;

istream& operator>>(istream& is, mint& x) {
    int X;
    is >> X;
    x = X;
    return is;
}
ostream& operator<<(ostream& os, mint& x) {
    os << x.val();
    return os;
}

// istream& operator<<(istream& is, mint &a) {
//     int x;
//     is >> x;
//     a = mint(x);
//     return is;
// }
// ostream& operator<<(ostream& os, mint a) {
//     os << a.val();
//     return os;
// }

// vector<mint> f = {1}, rf = {1};
// void init(int n) {
//     f.resize(n, 0);
//     rf.resize(n, 0);
//     f[0] = 1;
//     repi(i, 1, n) f[i] = (f[i - 1] * i);
//     repi(i, 0, n) rf[i] = f[i].inv();
// }
// mint P(int n, int k) {
//     assert(n>=k);
//     while(n > f.size()-1) {
//         f.push_back(f.back() * f.size());
//         rf.push_back(f.back().inv());
//     }
//     return f[n] * f[n-k];
// }
// mint C(int n, int k) {
//     assert(n>=k);
//     while(n > f.size()-1) {
//         f.push_back(f.back() * f.size());
//         rf.push_back(f.back().inv());
//     }
//     return f[n]*rf[n-k]*rf[k];
// }
// mint H(int n, int k) {
//     assert(n>=1);
//     return C(n+k-1, k);
// }
// mint Cat(int n) {
//     return C(2*n, n)-C(2*n, n-1);
// }

namespace internal {
    // @param n `0 <= n`
    // @return minimum non-negative `x` s.t. `n <= 2**x`
    int ceil_pow2(int n) {
        int x = 0;
        while ((1U << x) < (unsigned int)(n)) x++;
        return x;
    }

    // @param n `1 <= n`
    // @return minimum non-negative `x` s.t. `(n & (1 << x)) != 0`
    constexpr int bsf_constexpr(unsigned int n) {
        int x = 0;
        while (!(n & (1 << x))) x++;
        return x;
    }

    // @param n `1 <= n`
    // @return minimum non-negative `x` s.t. `(n & (1 << x)) != 0`
    int bsf(unsigned int n) {
    #ifdef _MSC_VER
        unsigned long index;
        _BitScanForward(&index, n);
        return index;
    #else
        return __builtin_ctz(n);
    #endif
    }
}  // namespace internal

template <class S, S (*op)(S, S), S (*e)()> struct segtree {
  public:
    segtree() : segtree(0) {}
    explicit segtree(int n) : segtree(std::vector<S>(n, e())) {}
    explicit segtree(const std::vector<S>& v) : _n((int)v.size()) {
        log = internal::ceil_pow2(_n);
        size = 1 << log;
        d = std::vector<S>(2 * size, e());
        for (int i = 0; i < _n; i++) d[size + i] = v[i];
        for (int i = size - 1; i >= 1; i--) {
            update(i);
        }
    }

    void set(int p, S x) {
        assert(0 <= p && p < _n);
        p += size;
        d[p] = x;
        for (int i = 1; i <= log; i++) update(p >> i);
    }

    S get(int p) const {
        assert(0 <= p && p < _n);
        return d[p + size];
    }

    S prod(int l, int r) const {
        assert(0 <= l && l <= r && r <= _n);
        S sml = e(), smr = e();
        l += size;
        r += size;

        while (l < r) {
            if (l & 1) sml = op(sml, d[l++]);
            if (r & 1) smr = op(d[--r], smr);
            l >>= 1;
            r >>= 1;
        }
        return op(sml, smr);
    }

    S all_prod() const { return d[1]; }

    template <bool (*f)(S)> int max_right(int l) const {
        return max_right(l, [](S x) { return f(x); });
    }
    template <class F> int max_right(int l, F f) const {
        assert(0 <= l && l <= _n);
        assert(f(e()));
        if (l == _n) return _n;
        l += size;
        S sm = e();
        do {
            while (l % 2 == 0) l >>= 1;
            if (!f(op(sm, d[l]))) {
                while (l < size) {
                    l = (2 * l);
                    if (f(op(sm, d[l]))) {
                        sm = op(sm, d[l]);
                        l++;
                    }
                }
                return l - size;
            }
            sm = op(sm, d[l]);
            l++;
        } while ((l & -l) != l);
        return _n;
    }

    template <bool (*f)(S)> int min_left(int r) const {
        return min_left(r, [](S x) { return f(x); });
    }
    template <class F> int min_left(int r, F f) const {
        assert(0 <= r && r <= _n);
        assert(f(e()));
        if (r == 0) return 0;
        r += size;
        S sm = e();
        do {
            r--;
            while (r > 1 && (r % 2)) r >>= 1;
            if (!f(op(d[r], sm))) {
                while (r < size) {
                    r = (2 * r + 1);
                    if (f(op(d[r], sm))) {
                        sm = op(d[r], sm);
                        r--;
                    }
                }
                return r + 1 - size;
            }
            sm = op(d[r], sm);
        } while ((r & -r) != r);
        return 0;
    }

  private:
    int _n, size, log;
    std::vector<S> d;

    void update(int k) { d[k] = op(d[2 * k], d[2 * k + 1]); }
};

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

const int N = 200100;

void solve() {
    int h, w, n, p;
    cin >> h >> w >> n >> p;
    vi x(n), y(n);
    FOR(n) cin >> x[i] >> y[i];

    vector<int> order(n);
    iota(all(order), 0);
    sort(all(order), [&](int i, int j) {
        if(x[i] != x[j]) return x[i] < x[j];
        return y[i] < y[j];
    });

    segtree<S, op, e> seg(N);

    for(int i : order) {
        int cur = seg.get(y[i]);
        int mx = seg.prod(0, y[i]+1);
        seg.set(y[i], max(cur, mx)+1);
    }

    int many = seg.prod(0, N);

    mint ans = 1;
    mint p_inv = mint(p).inv();
    ans = (-(p_inv-1)).pow(h+w-3-many)*(-(p_inv*2-1)).pow(many);

    cout << (-(ans-1)).val() << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}