#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define INF 1000000000
int n;
vector<vector<int>> v;
vector<vector<int>> up;
vector<int> pr, sp, de;
void prec(int x, int p){
de[x] = de[p] + 1;
for (auto el : v[x]){
if (el != p) prec(el, x);
}
}
void dfs(int x, int p){
pr[x] ^= pr[p];
for (auto el : v[x]){
if (el != p){
dfs(el, x);
}
}
}
void calc(int x, int p, int wh){
if (p != 0) up[wh][x] = up[wh][p] + 1;
for (auto &el : v[x]){
if (el != p) calc(el, x, wh);
}
}
int dist(int a, int b){
if (sp[b] != 0) swap(a, b);
return up[sp[a]][b];
}
int check(int a, int b, int mask){
return (((pr[a] ^ pr[b]) | mask) == mask);
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int s, t, a, b, w, m = 0, cc = 3;
cin>>n;
cin>>s>>t;
v.assign(n + 1, vector<int>()), de.assign(n + 1, 0);
up.assign(23, vector<int>(n + 1, 0));
pr.assign(n + 1, 0), sp.assign(n + 1, 0);
sp[s] = 1; sp[t] = 2;
vector<vector<int>> al;
for (int i = 0; i < n - 1; i++){
cin>>a>>b>>w;
if (w == 0){
v[a].push_back(b);
v[b].push_back(a);
}
else{
v[a].push_back(b);
v[b].push_back(a);
al.push_back({a, b, w});
if (sp[w] == 0) sp[w] = cc++;
m++;
}
}
prec(1, 0);
for (int i = 0; i < m; i++){
if (de[al[i][0]] < de[al[i][1]]) pr[al[i][1]] += (1<<i);
else pr[al[i][0]] += (1<<i);
}
dfs(1, 0);
for (int i = 1; i <= n; i++){
if (sp[i] == 0) continue;
calc(i, 0, sp[i]);
}
int ans = INF;
if (check(s, t, 0) == 1) ans = dist(s, t);
int ti = (1<<m);
vector<vector<int>> dp(ti, vector<int>(m, INF));
vector<int> wh(m + 1, 0);
for (int i = 0; i < m; i++){
if (check(al[i][2], s, 0) == 1) dp[(1<<i)][i] = dist(al[i][2], s);
if (dist(al[i][2], al[i][0]) < dist(al[i][2], al[i][1])){
wh[i] = al[i][0];
}
else wh[i] = al[i][1];
}
vector<int> us(m + 1, 0), nus(m + 1, 0);
for (int i = 1; i < ti; i++){
int c0 = 0, c1 = 0, el = 0, val = 0;
for (int j = 0; j < m; j++){
int val = (i & (1<<j));
if (val != 0) us[c0++] = j;
else nus[c1++] = j;
}
for (int j = 0; j < c0; j++){
el = us[j];
int cur = wh[el];
if (check(cur, al[el][2], i) == 0){
dp[i][el] = INF;
continue;
}
else dp[i][el] += dist(cur, al[el][2]);
if (check(cur, t, i) == 1) ans = min(ans, dp[i][el] + dist(cur, t));
for (int k = 0; k < c1; k++){
val = nus[k];
int to = (i | (1<<val));
if (check(cur, al[val][2], i) == 1){
dp[to][val] = min(dp[to][val], dp[i][el] + dist(al[val][2], cur));
}
}
}
}
if (ans >= INF) cout<<-1;
else cout<<ans;
}
