/*
in the name of god
*/
//#pragma GCC optimize("Ofast,O3,unroll-loops")
//#pragma GCC target("avx,avx2,fma")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,sse4a,avx,avx2,popcnt,tune=native")
#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> pii;
typedef pair<long long ,long long> pll;
typedef long long ll ;
#define File freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout);
#define all(V) V.begin(),V.end()
#define setprec(x) fixed << setprecision(x)
#define Mp(a,b) make_pair(a,b)
#define len(V) (int)(V.size())
#define sep ' '
#define endl '\n'
#define pb push_back
#define fi first
#define sec second
#define popcount(x) __builtin_popcount(x)
#define lid u<<1
#define rid (lid)|1
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const ll N = 1e6 + 10,M=22,SQ=320,LOG=21;
const ll inf = 1e16 , MD = 1e9 + 7;
inline ll md(ll x){ x %= MD; return (x < 0 ? x + MD : x);}
int n , m;
vector<pii> g[N];
vector<pair<pii,int>> E;
int s,t;
int par[N][LOG];
int ps[N];
int dis[N];
int F[M][M];
int D[M][M];
int dp[1<<21][M];
void dfs(int u,int p){
par[u][0] = p;
dis[u] = (u == p ? 0 : dis[p] + 1);
for(int j=1 ; j < LOG;j++) par[u][j] = par[par[u][j-1]][j-1];
for(auto h : g[u]){
if(h.fi != p){
ps[h.fi] = ps[u] ^ h.sec;
dfs(h.fi,u);
}
}
}
int lift(int u,int k){
for(int j = 0 ; j < LOG;j++)
if(k&(1<<j)) u = par[u][j];
return u;
}
int lca(int u,int v){
if(dis[u] > dis[v]) swap(u,v);
v = lift(v,dis[v] - dis[u]);
if(u==v) return u;
for(int j =LOG-1;j >= 0;j--)
if(par[u][j]^par[v][j])
u = par[u][j],v=par[v][j];
return par[u][0];
}
int DIS(int u,int v){
return dis[u] + dis[v] - 2*dis[lca(u,v)];
}
int calc(int u,int v){
return (ps[u] ^ ps[v]);
}
int32_t main() {
ios_base::sync_with_stdio(false);cout.tie(0);cin.tie(0);
cin >> n ;
cin >> s >> t;
for(int i = 0 ; i < n - 1;i++){
int u,v,w;
cin >> u >> v >> w;
int w2 = (w == 0 ? 0 : (1<<m));
if(w) m++;
g[u].pb({v,w2});
g[v].pb({u,w2});
if(w) E.pb({{u,v},w});
}
dfs(s,s);
for(int i = 0;i < m;i++){
if(par[E[i].fi.sec][0] != E[i].fi.fi) swap(E[i].fi.sec,E[i].fi.fi);
}
for(int i = 0 ; i < m;i++){
for(int j = 0; j < m;j++){
F[i][j] = calc(E[i].sec,E[j].fi.fi);
D[i][j] = DIS(E[i].sec,E[j].fi.fi);
}
}
for(int mask = 0;mask < (1<<m);mask++){
for(int i = 0; i < m;i++) dp[mask][i] = inf;
}
for(int i = 0; i < m ;i++){
if(F[i][i] == 0) dp[1<<i][i] = dis[E[i].sec] + D[i][i];
}
for(int mask = 0;mask < (1<<m);mask++){
if(popcount(mask) <= 1) continue;
for(int i = 0; i < m ;i++){
if(mask&(1<<i)){
int nmask = mask^(1<<i);
for(int j = 0 ; j < m;j++){
if(mask&(1<<j) && j != i){
int tmp = D[i][j] + D[i][i] + dp[nmask][j];
if(((F[i][j]&nmask) == F[i][j]) && ((F[i][i]&nmask) == F[i][i])) dp[mask][i] = min(dp[mask][i],tmp);
}
}
}
}
}
int ans = inf;
for(int mask = 0;mask < (1<<m);mask++){
for(int i = 0; i < m;i++){
if(mask&(1<<i)){
if((calc(E[i].fi.fi,t)&mask) == calc(E[i].fi.fi,t)) ans = min(ans,dp[mask][i] + DIS(t,E[i].fi.fi));
}
}
}
if(ans == inf) cout << -1 << endl;
else cout << ans << endl;
return 0;
}
