#include "closing.h"
#include <bits/stdc++.h>
using namespace std;
#define sp " "
#define endl "\n"
#define fastio() cin.tie(0), ios_base::sync_with_stdio(0)
#define fileio() freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout)
#define pb push_back
#define pii pair<int, int>
#define st first
#define nd second
#define LL node * 2
#define RR node * 2 + 1
#define ll long long
const int modulo = 1e9 + 7;
const ll INF = 2e18 + 7;
int max_score(int N, int X, int Y, long long K, vector<int> U, vector<int> V, vector<int> W)
{
vector<pii> adj[N + 5];
vector<ll> dist1(N, -1), dist2(N, -1);
vector<ll> par1(N, -1), par2(N, -1);
for (ll i = 0; i < N - 1; i++){
adj[U[i]].pb({V[i], W[i]});
adj[V[i]].pb({U[i], W[i]});
}
priority_queue<pair<ll, ll>> q;
q.push({0, X});
while(!q.empty()){
pii tmp = q.top();
q.pop();
ll top = tmp.nd, d = -tmp.st;
dist1[top] = d;
for (auto i : adj[top]){
ll v = i.st, w = i.nd;
if (dist1[v] != -1) continue;
par1[v] = top;
q.push({-(d + w), v});
}
}
q.push({0, Y});
ll ans = 0;
while(!q.empty()){
pii tmp = q.top();
q.pop();
ll top = tmp.nd, d = -tmp.st;
dist2[top] = d;
for (auto i : adj[top]){
ll v = i.st, w = i.nd;
if (dist2[v] != -1) continue;
par2[v] = top;
q.push({-(d + w), v});
}
}
for(ll i = 0; i < (1<<N); i++){
vector<ll> v;
ll sum = 0, res = 0;
for (ll j = 0; j < N; j++){
if (i & (1<<j)){
res++;
if (dist1[j] > dist2[j]) swap(dist1[j], dist2[j]), swap(par1[j], par2[j]);
if (par1[j] == -1 || (i & (1<<par1[j]))){
sum += dist1[j];
if (par2[j] == -1 || (i & (1<<par2[j]))){
v.pb(dist2[j] - dist1[j]);
}
}
else if (par2[j] == -1 || (i & (1<<par2[j]))){
sum += dist2[j];
}
else{
sum = K + 1;
}
}
}
sort(v.begin(), v.end());
ll it = 0;
while(it < v.size() && sum + v[it] <= K) {
sum += v[it], res++;
it++;
}
if (sum <= K) ans = max(ans, res);
}
return ans;
}
/*
int main()
{
fileio();
int Q;
assert(1 == scanf("%d", &Q));
std::vector<int> N(Q), X(Q), Y(Q);
std::vector<long long> K(Q);
std::vector<std::vector<int>> U(Q), V(Q), W(Q);
for (int q = 0; q < Q; q++)
{
assert(4 == scanf("%d %d %d %lld", &N[q], &X[q], &Y[q], &K[q]));
U[q].resize(N[q] - 1);
V[q].resize(N[q] - 1);
W[q].resize(N[q] - 1);
for (int i = 0; i < N[q] - 1; ++i)
{
assert(3 == scanf("%d %d %d", &U[q][i], &V[q][i], &W[q][i]));
}
}
fclose(stdin);
std::vector<int> result(Q);
for (int q = 0; q < Q; q++)
{
result[q] = max_score(N[q], X[q], Y[q], K[q], U[q], V[q], W[q]);
}
for (int q = 0; q < Q; q++)
{
printf("%d\n", result[q]);
}
fclose(stdout);
return 0;
}
*/
