#include<bits/stdc++.h>
#define MASK(i) (1 << (i))
#define pub push_back
#define all(v) v.begin(), v.end()
#define compact(v) v.erase(unique(all(v)), end(v))
#define pii pair<int,int>
#define fi first
#define se second
#define endl "\n"
#define sz(v) (int)(v).size()
#define dbg(x) "[" #x " = " << (x) << "]"
#define vi vector<int>
using namespace std;
template<class T> bool minimize(T& a, T b){if(a > b) return a = b, true;return false;}
template<class T> bool maximize(T& a, T b){if(a < b) return a = b, true;return false;}
typedef long long ll;
typedef long double ld;
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r){return uniform_int_distribution<ll>(l, r)(rng);}
const int MAX = 4e6 + 15;
const int INF = 1e9;
struct DSU{
int n;
vector<int> lab;
stack<pair<int&, int>> history;
DSU(int n) : n(n), lab(n + 5, -1) {}
//asce optimization -> peak
int asc(int u, bool roll){
return (lab[u] < 0) ? u : (!roll) ? lab[u] = asc(lab[u], roll) : asc(lab[u], roll);
}
void join(int u, int v, bool roll){
u = asc(u, roll), v = asc(v, roll);
if(u == v) return;
if(lab[u] > lab[v]) swap(u, v);
if(roll){
history.push({lab[u], lab[u]});
history.push({lab[v], lab[v]});
}
lab[u] += lab[v];
lab[v] = u;
}
int snap() {return sz(history);}
bool same(int u, int v, bool roll){
return asc(u, roll) == asc(v, roll);
}
void rollback(int snapshot){
assert(snap() >= snapshot);
while(snap() > snapshot){
history.top().fi = history.top().se;
history.pop();
}
}
};
int n, m, S, T;
//u: 0, v: 1, key: 2
vector<array<int, 3>> edges;
vector<int> g[MAX];
int tin[MAX], euler[MAX], timer;
int h[MAX];
void dfs(int u, int p){
euler[tin[u] = ++timer] = u;
for(int v : g[u]) if(v != p){
h[v] = h[u] + 1;
dfs(v, u);
euler[++timer] = u;
}
}
int spt[MAX][21];
void prepareLCA(){
int lg = 31 - __builtin_clz(timer);
for(int i = 1; i <= timer; i++) spt[i][0] = i;
for(int j = 1; j <= lg; j++){
for(int i = 1; i + (1 << j) - 1 <= timer; i++){
int a = spt[i][j-1];
int b = spt[i + (1 << (j-1))][j-1];
spt[i][j] = (h[euler[a]] < h[euler[b]]) ? a : b;
}
}
}
int lca(int u, int v){
int l = tin[u], r = tin[v];
if(l > r) swap(l, r);
int k = 31 - __builtin_clz(r - l + 1);
int a = spt[l][k];
int b = spt[r - (1 << k) + 1][k];
return (h[euler[a]] < h[euler[b]]) ? euler[a] : euler[b];
}
int dist(int u, int v){
return h[u] + h[v] - 2*h[lca(u, v)];
}
//minimum cost to go to vertex U from S, unlock edges in mask
int dp[1 << 20][20][2];
void solve(){
cin >> n >> S >> T;
DSU dsu(n);
for(int i = 1; i < n; i++){
int u, v, w; cin >> u >> v >> w;
g[u].push_back(v);
g[v].push_back(u);
if(!w){
dsu.join(u, v, false);
}
else{
edges.push_back({u, v, w});
}
}
dfs(1, -1);
prepareLCA();
if(dsu.same(S, T, false)){
cout << dist(S, T) << endl;
return;
}
m = sz(edges);
for(int mask = 0; mask < (1 << m); mask++){
for(int i = 0; i < m; i++){
for(int j = 0; j < 2; j++){
dp[mask][i][j] = INF;
}
}
}
for(int i = 0; i < m; i++){
if(dsu.same(S, edges[i][2], false)){//get the key without unlock
for(int j = 0; j < 2; j++){
if(dsu.same(S, edges[i][j], false)){//S -> key -> U
dp[1 << i][i][j] = dist(S, edges[i][2]) + dist(edges[i][2], edges[i][j]);
}
}
}
}
//asce optimization 2:
for(int i = 1; i <= n; i++) dsu.asc(i, false);
int answer = INF;
for(int mask = 1; mask < (1 << m); mask++){
int big_snap = dsu.snap();
vector<int> lock, unlock;
for(int i = 0; i < m; i++){
if(mask >> i & 1){
unlock.push_back(i);
dsu.join(edges[i][0], edges[i][1], true);
}
else{
lock.push_back(i);
}
}
//1 case: S, T in same component after unlock edges in mask
if(dsu.same(S, T, true)){
for(int i : unlock){
for(int j = 0; j < 2; j++){
minimize(answer, dp[mask][i][j] + dist(edges[i][j], T));
}
}
}
for(int idF : unlock){
for(int i = 0; i < 2; i++){
if(dp[mask][idF][i] == INF) continue;
for(int idS : lock){
for(int j = 0; j < 2; j++){
int u, v, key; tie(u, v, key) = {edges[idF][i], edges[idS][j], edges[idS][2]};
if(!dsu.same(u, key, true) || !dsu.same(key, v, true)) continue;
minimize(dp[mask | (1 << idS)][idS][j], dp[mask][idF][i] + dist(u, key) + dist(key, v));
}
}
}
}
dsu.rollback(big_snap);
}
cout << (answer != INF ? answer : -1) << endl;
}
signed main(){
ios_base::sync_with_stdio(NULL);
cin.tie(0); cout.tie(0);
#define task "task"
if(fopen(task".INP", "r")){
freopen(task".INP", "r", stdin);
freopen(task".OUT", "w", stdout);
}
int t; t = 1; //cin >> t;
while(t--) solve();
}
