#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
#define F first
#define S second
const int N = 1e6 + 60;
const int MSK = (1<<20) + 60;
const int M = 24;
const int INF = 1e9 + 9;
ll mvcnt = 0;
vector <int> adj[N];
int key[M];
int lok[M];
int Disk[M][N];
int Wk[M][M];//key -> lock
int dp[M][MSK];
int eg[M];
int teg[M][2];
int Wisk[N];
int Dt[N];
struct tii{
int u;
int v;
int w;
};
int ck = 0;
int cms = 0;
int n, s, t;
void dfs(int u, int fa){
//mvcnt++;
Disk[ck][u] = Disk[ck][fa] + 1;
if (u > n){
Disk[ck][u]--;
cms |= (1<<(u-n-1));
Wk[ck][u-n-1] = cms;
}
for (int v:adj[u]){
mvcnt++;
if (v != fa)
dfs(v, u);
}
if (u > n)
cms ^= (1<<(u-n-1));
}
void dtfs(int u, int fa){
//mvcnt++;
Wisk[u] = Wisk[fa];
Dt[u] = Dt[fa] + 1;
if (u > n){
Dt[u]--;
Wisk[u] |= (1<<(u-n-1));
}
for (int v:adj[u]){
//mvcnt++;
if (v != fa)
dtfs(v, u);
}
}
vector <tii> q;
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> s >> t;
int k = 0;
for (int i=1;i<n;i++){
int u, v, w;
cin >> u >> v >> w;
if (w == 0)
w = -1;
q.push_back({u, v, w});
}
for (auto [u, v, w]:q){
if (w != -1){
mvcnt++;
key[k] = w;
teg[k][0] = u;
teg[k][1] = v;
k++;
adj[u].push_back(n+k); adj[n+k].push_back(u);
adj[n+k].push_back(v); adj[v].push_back(n+k);
}
else {
adj[u].push_back(v); adj[v].push_back(u);
}
}
Dt[n+k+1] = -1;
dtfs(s, n+k+1);
for (int i=0;i<k;i++){
if (Dt[teg[i][0]] > Dt[teg[i][1]])
eg[i] = teg[i][1];
else
eg[i] = teg[i][0];
}
for (int i=0;i<k;i++){
ck = i;
Disk[i][n+k+1] = -1;
dfs(key[i], n+k+1);
}
Dt[n+k+1] = -1;
dtfs(t, n+k+1);
int msk = 1 << k;
int mvvv = 0;
for (int ms=msk-1;ms>0;ms--){ //msk //i: eg[i] <- ma & klid haye msk ro dareim
int ci = ms;
mvvv++;
while (ci){
mvvv += 3;
int i = __builtin_ctz(ci);
ci ^= (1 << i);
if ((Wisk[eg[i]] & ms) == Wisk[eg[i]]){
dp[i][ms] = Dt[eg[i]];
continue;
}
mvvv += 2;
dp[i][ms] = INF;
int cm = msk - 1 - ms;
while (cm){
mvvv += 5;
int j = __builtin_ctz(cm);
int jb = (1 << j);
cm ^= jb;
if (((Wk[j][i] & ms) == Wk[j][i]) && ((Wk[j][j] & (ms|jb)) == Wk[j][j]))
dp[i][ms] = min(dp[i][ms], Disk[j][eg[i]] + Disk[j][eg[j]] + dp[j][ms | jb]);
}
}
}
dtfs(s, n+k+1);
if (Wisk[t] == 0){
cout << Dt[t] << '\n';
return 0;
}
int ans = INF;
for (int i=0;i<k;i++){
int sb = Wisk[eg[i]];
if (Wisk[key[i]] == 0 && (sb & (1 << i)) == sb){
ans = min(ans, dp[i][1<<i] + Disk[i][s] + Disk[i][eg[i]]);
}
}
//mvcnt /= 10000000;
///exit(mvcnt);
if (ans == INF)
cout << -1 << '\n';
else
cout << ans << '\n';
}
