/*
ID: Victor Chen [mail_vi1]
PROG: Closing Time
LANG: C++
*/

#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <vector>

#define INF 0x3f3f3f3f

using namespace std;

typedef long long ll;

const int Maxn = 2e5;

class Graph
{
    public:
        int cnt, head[Maxn+10];
        struct Edge
        {
            int to, nxt;
            int val;
        }p[2*Maxn+10];

        int root;
        int dep[Maxn+10], fa[Maxn+10];
        ll val[Maxn+10];

        void AddEdge(int x, int y, int v)
        {
            cnt++;
            p[cnt].to = y;
            p[cnt].val = v;

            p[cnt].nxt = head[x];
            head[x] = cnt;
        }

        void dfs(int x)
        {
            for(int i=head[x]; i!=0; i=p[i].nxt)
                if(dep[p[i].to] == 0)
                {
                    dep[p[i].to] = dep[x] + 1;
                    fa[p[i].to] = x;
                    val[p[i].to] = val[x] + p[i].val;
                    dfs(p[i].to);
                }
        }

        void clear()
        {
            cnt = 0;
            memset(head, 0, sizeof(head));
        }

        void init(int x)
        {
            root = x;
            memset(dep, 0, sizeof(dep));
            dep[root] = 1;
            fa[root] = 0;
            val[root] = 0;

            dfs(root);
        }
}g;

int n;
int c1, c2;

ll cst;

ll val[Maxn+10];

struct Pair
{
    int id;
    ll dis;

    Pair(){}
    Pair(int id, ll dis)
    {
        this->id = id;
        this->dis = dis;
    }

    bool operator < (const Pair &x) const
    {
        return x.dis < dis;
    }
};

priority_queue<Pair> q;

int max_score(int N, int X, int Y, ll K, vector<int> U, vector<int> V, vector<int> W)
{
    int ans = 0;

    memset(val, INF, sizeof(val));

    g.clear();

    n = N, c1 = X, c2 = Y;
    for(int i=0; i<n-1; i++)
    {
        g.AddEdge(U[i], V[i], W[i]);
        g.AddEdge(V[i], U[i], W[i]);
    }

    // Case 1: If only consider without connections.
    g.init(c1);
    for(int i=1; i<=n; i++)
        val[i] = min(val[i], g.val[i]);
    g.init(c2);
    for(int i=1; i<=n; i++)
        val[i] = min(val[i], g.val[i]);

    cst = 0;
    sort(val+1, val+n+1);
    for(int i=1; i<=n; i++)
        if(cst + val[i] <= K)
            cst += val[i], ans++;
        else
            break;
    
    return ans;
}

// int T;
// int N, X, Y;
// ll K;
// vector<int> U, V, W;

// int main()
// {
//     scanf("%d", &T);
//     while(T != 0)
//     {
//         T--;
//         scanf("%d%d%d%lld", &N, &X, &Y, &K);
//         for(int i=0; i<N-1; i++)
//         {
//             int x, y, z;
//             scanf("%d%d%d", &x, &y, &z);
//             U.push_back(x); V.push_back(y); W.push_back(z);
//         }

//         printf("%d\n", max_score(N, X, Y, K, U, V, W));
//     }

//     return 0;
// }