#include <bits/stdc++.h>
// #include <coding_library/graph/maxflow.hpp>

using namespace std;

template<typename T1, typename T2>
ostream& operator<<(ostream& out, const pair<T1, T2>& x) {
    return out << x.first << ' ' << x.second;
}

template<typename T1, typename T2>
istream& operator>>(istream& in, pair<T1, T2>& x) {
    return in >> x.first >> x.second;
}

template<typename T>
istream& operator>>(istream& in, vector<T>& a) {
    for(auto& x: a) {
        in >> x;
    }
    return in;
};

template<typename T>
ostream& operator<<(ostream& out, const vector<T>& a) {
    for(auto x: a) {
        out << x << ' ';
    }
    return out;
};

template<class T>
class MaxFlow {
  private:
    struct Edge {
        T flow, cap;
        int idx, rev, to;
        Edge(int _to, int _rev, T _flow, T _cap, int _idx)
            : to(_to), rev(_rev), flow(_flow), cap(_cap), idx(_idx) {}
    };

    vector<int> dist, po;
    int n;

    bool bfs(int s, int t) {
        fill(dist.begin(), dist.end(), -1);
        fill(po.begin(), po.end(), 0);

        queue<int> q;
        q.push(s);
        dist[s] = 0;

        while(!q.empty()) {
            int u = q.front();
            q.pop();

            for(Edge e: adj[u]) {
                if(dist[e.to] == -1 && e.flow < e.cap) {
                    dist[e.to] = dist[u] + 1;
                    q.push(e.to);
                }
            }
        }
        return dist[t] != -1;
    }

    T dfs(int u, int t, T fl = INF) {
        if(u == t) {
            return fl;
        }

        for(; po[u] < (int)adj[u].size(); po[u]++) {
            auto& e = adj[u][po[u]];
            if(dist[e.to] == dist[u] + 1 && e.flow < e.cap) {
                T f = dfs(e.to, t, min(fl, e.cap - e.flow));
                e.flow += f;
                adj[e.to][e.rev].flow -= f;
                if(f > 0) {
                    return f;
                }
            }
        }

        return 0;
    }

  public:
    const static T INF = numeric_limits<T>::max();

    MaxFlow(int n = 0) { init(n); }

    vector<vector<Edge>> adj;

    void init(int _n) {
        n = _n;
        adj.assign(n + 1, {});
        dist.resize(n + 1);
        po.resize(n + 1);
    }

    void add_edge(int u, int v, T w, int idx = -1) {
        adj[u].push_back(Edge(v, adj[v].size(), 0, w, idx));
        adj[v].push_back(Edge(u, adj[u].size() - 1, 0, 0, -1));
    }

    T flow(int s, int t) {
        assert(s != t);

        T ret = 0, to_add;
        while(bfs(s, t)) {
            while((to_add = dfs(s, t))) {
                ret += to_add;
            }
        }

        return ret;
    }
};

int n, m, jump_d, w;
vector<tuple<int, int, int>> rubish;

void read() {
    cin >> n >> m >> jump_d >> w;
    rubish.resize(n);
    for(auto& [x, y, z]: rubish) {
        cin >> x >> y >> z;
    }
}

void solve() {
    if(jump_d >= w) {
        cout << 1 << '\n';
        return;
    }

    int max_ans = n + 1 + m;
    int num_vers = 2 + max_ans * 2 * n, source = num_vers - 2, sink = num_vers - 1;

    function<int(int, int, int)> encode_state = [&](int t, int i,
                                                    int in_out_flag) -> int {
        return t * 2 * n + 2 * i + in_out_flag;
    };

    MaxFlow<int> mf(num_vers);

    int flow = 0;
    for(int t = 0; t < max_ans; t++) {
        for(int i = 0; i < n; i++) {
            auto [x, y, c] = rubish[i];
            if(y <= jump_d) {
                mf.add_edge(source, encode_state(t, i, 0), MaxFlow<int>::INF);
            }
            mf.add_edge(encode_state(t, i, 0), encode_state(t, i, 1), c);
            if(y + jump_d >= w) {
                mf.add_edge(encode_state(t, i, 1), sink, MaxFlow<int>::INF);
            }

            if(t > 0) {
                for(int j = 0; j < n; j++) {
                    auto [x2, y2, _] = rubish[j];
                    if((x - x2) * 1ll * (x - x2) + (y - y2) * 1ll * (y - y2) <=
                       jump_d * 1ll * jump_d) {
                        mf.add_edge(
                            encode_state(t - 1, j, 1), encode_state(t, i, 0),
                            MaxFlow<int>::INF
                        );
                    }
                }
            }
        }

        flow += mf.flow(source, sink);
        if(flow >= m) {
            cout << t + 2 << '\n';
            return;
        }
    }

    cout << "IMPOSSIBLE\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int T = 1;
    // cin >> T;
    for(int test = 1; test <= T; test++) {
        read();
        // cout << "Case #" << test << ": ";
        solve();
    }

    return 0;
}
