#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MOD = 1000000007;

template <class S, S (*op)(S, S), S (*e)(), class C = long long int> struct segtree2D_lite {
    int H, logH;
    std::vector<int> logW, W;
    std::vector<C> Yc;
    std::vector<std::vector<int>> parent;
    std::vector<std::vector<std::pair<int, int>>> child;
    std::vector<std::vector<C>> Xc;
    std::vector<std::pair<C, C>> preorder;
    std::vector<std::vector<S>> d;
    segtree2D_lite()  {}
    void insert(C y, C x){
        preorder.emplace_back(y, x);
    }
    void build(){
        std::sort(preorder.begin(), preorder.end());
        Yc.resize(preorder.size());
        for(int i = 0; i < (int)(preorder.size()); i++)Yc[i] = preorder[i].first;
        Yc.erase(std::unique(Yc.begin(), Yc.end()), Yc.end());
        logH = ceil_pow2(Yc.size());
        H = 1 << logH;
        Xc.resize(2 * H), d.resize(2 * H);
        logW.resize(2 * H), W.resize(2 * H);
        parent.resize(2 * H), child.resize(H);
        for(int i = 0, y_id = 0; i < (int)(preorder.size()); i++){
            while(Yc[y_id] < preorder[i].first)y_id++;
            Xc[y_id + H].emplace_back(preorder[i].second);
        }
        for(int y = 2 * H - 1; y >= H; y--){
            Xc[y].erase(std::unique(Xc[y].begin(), Xc[y].end()), Xc[y].end());
            parent[y].resize(Xc[y].size());
            logW[y] = ceil_pow2(Xc[y].size());
            W[y] = 1 << logW[y];
            d[y].resize(2 * W[y], e());
        }
        for(int y = H - 1; y >= 1; y--){
            int Ly_id = 2 * y, Ry_id = 2 * y + 1;
            int Lx_id = 0, Rx_id = 0;
            while(Lx_id < Xc[Ly_id].size() && Rx_id < Xc[Ry_id].size()){
                if(Xc[Ly_id][Lx_id] == Xc[Ry_id][Rx_id]){
                    parent[Ly_id][Lx_id] = parent[Ry_id][Rx_id] = Xc[y].size();
                    Xc[y].emplace_back(Xc[Ly_id][Lx_id]);
                    child[y].emplace_back(Lx_id + W[Ly_id], Rx_id + W[Ry_id]);
                    Lx_id++, Rx_id++;
                }else if(Xc[Ly_id][Lx_id] < Xc[Ry_id][Rx_id]){
                    parent[Ly_id][Lx_id] = Xc[y].size();
                    Xc[y].emplace_back(Xc[Ly_id][Lx_id]);
                    child[y].emplace_back(Lx_id + W[Ly_id], 0);
                    Lx_id++;
                }else{
                    parent[Ry_id][Rx_id] = Xc[y].size();
                    Xc[y].emplace_back(Xc[Ry_id][Rx_id]);
                    child[y].emplace_back(0, Rx_id + W[Ry_id]);
                    Rx_id++;
                }
            }
            while(Lx_id < Xc[Ly_id].size()){
                parent[Ly_id][Lx_id] = Xc[y].size();
                Xc[y].emplace_back(Xc[Ly_id][Lx_id]);
                child[y].emplace_back(Lx_id + W[Ly_id], 0);
                Lx_id++;
            }
            while(Rx_id < Xc[Ry_id].size()){
                parent[Ry_id][Rx_id] = Xc[y].size();
                Xc[y].emplace_back(Xc[Ry_id][Rx_id]);
                child[y].emplace_back(0, Rx_id + W[Ry_id]);
                Rx_id++;
            }
            parent[y].resize(Xc[y].size());
            logW[y] = ceil_pow2(Xc[y].size());
            W[y] = 1 << logW[y];
            d[y].resize(2 * W[y], e());
        }
    }
    void set(C py, C px, S v){
        int y = std::lower_bound(Yc.begin(), Yc.end(), py) - Yc.begin();
        y += H;
        int x = std::lower_bound(Xc[y].begin(), Xc[y].end(), px) - Xc[y].begin(), nxt_x = parent[y][x];
        x += W[y];
        d[y][x] = v;
        while(x >>= 1)updateX(y, x);
        while(y >>= 1){
            x = nxt_x, nxt_x = parent[y][x];
            d[y][x + W[y]] = op(d[2 * y][child[y][x].first], d[2 * y + 1][child[y][x].second]);
            x += W[y];
            while(x >>= 1)updateX(y, x);
        }
    }
    S get(C py, C px){
        int y = std::lower_bound(Yc.begin(), Yc.end(), py) - Yc.begin();
        y += H;
        int x = std::lower_bound(Xc[y].begin(), Xc[y].end(), px) - Xc[y].begin();
        return d[y][x + W[y]];
    }
    S prod(C lpy, C lpx , C rpy , C rpx){
        int ly = std::lower_bound(Yc.begin(), Yc.end(), lpy) - Yc.begin();
        int ry = std::lower_bound(Yc.begin(), Yc.end(), rpy) - Yc.begin();
        S sml = e(), smr = e();
        ly += H, ry += H ;
        while (ly < ry) {
            if (ly & 1) sml = op(sml, yline_prod(lpx, rpx , ly++));
            if (ry & 1) smr = op(yline_prod(lpx, rpx , --ry), smr);
            ly >>= 1, ry >>= 1;
        }
        return op(sml, smr);
    }
    S yline_prod(C lpx, C rpx , int y){
        int lx = std::lower_bound(Xc[y].begin(), Xc[y].end(), lpx) - Xc[y].begin();
        int rx = std::lower_bound(Xc[y].begin(), Xc[y].end(), rpx) - Xc[y].begin();
        S sml = e(), smr = e();
        lx += W[y], rx += W[y] ;
        while (lx < rx) {
            if (lx & 1) sml = op(sml, d[y][lx++]);
            if (rx & 1) smr = op(d[y][--rx], smr);
            lx >>= 1, rx >>= 1;
        }
        return op(sml, smr);
    }
    private:
    int ceil_pow2(int n) {
        int x = 0;
        while ((1U << x) < (unsigned int)(n)) x++;
        return x;
    }
    void updateX(int yi, int xi) { d[yi][xi] = op(d[yi][2 * xi], d[yi][2 * xi + 1]); }
};

ll op(ll lhs, ll rhs){
    return lhs + rhs;
}
ll e(){return 0;}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll N, K, L, P;
    cin >> N >> K >> L >> P;
    int n1 = N / 2, n2 = N - n1;
    vector<ll> a(N), b(N);
    for(int i = 0; i < N; i++)cin >> a[i] >> b[i];
    vector<vector<pair<ll,ll>>> c(n1 + 1), d(n2 + 1);
    segtree2D_lite<ll, op, e> seg;
    for(int i = 0; i < (1 << n1); i++){
        ll s1 = 0, s2 = 0;
        for(int j = 0; j < n1; j++){
            if(i >> j & 1){
                s1 += a[j];
                s2 += b[j];
            }
        }
        c[__builtin_popcount(i)].emplace_back(s1, s2);
    }

    for(int i = 0; i < (1 << n2); i++){
        ll s1 = 0, s2 = 0;
        for(int j = 0; j < n2; j++){
            if(i >> j & 1){
                s1 += a[j + n1];
                s2 += b[j + n1];
            }
        }
        d[__builtin_popcount(i)].emplace_back(s1, s2);
        seg.insert(s1, s2);
    }
    seg.build();

    ll ans = 0;
    for(int ci = min(n1, int(K)), di = 0; ci >= 0; ci--){
        while(di <= n2 && ci + di <= K){
            for(auto &&p:d[di]){
                seg.set(p.first, p.second, seg.get(p.first, p.second) + 1);
            }
            di++;
        }
        //cerr << cnt << " " << seg.d[1][1] << '\n';
        //assert(cnt == seg.d[1][1]);
        for(auto &&p:c[ci]){
            ll ly = 0, ry = L + 1 - p.first;
            if(ry <= ly)continue;
            ans += seg.prod(ly, P - p.second, ry, 1ll << 62);
        }
    }
    cout << ans << '\n';
}