#include <bits/stdc++.h>
//#pragma GCC optimize ("Ofast,unroll-loops")
//#pragma GCC target ("avx2")
using namespace std;
typedef long long ll;
typedef pair<int, int> pp;
#define rep(i,l,r) for(int i = (l); i < (r); i++)
#define per(i,r,l) for(int i = (r); i >= (l); i--)
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
#define pb push_back
#define ff first
#define ss second
void dbg(){
cerr << endl;
}
template<typename Head, typename... Tail> void dbg(Head h, Tail... t){
cerr << " " << h << ",";
dbg(t...);
}
#define er(...) cerr << __LINE__ << " <" << #__VA_ARGS__ << ">:", dbg(__VA_ARGS__)
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
void IOS(){
cin.tie(0) -> sync_with_stdio(0);
// #ifndef ONLINE_JUDGE
// freopen("inp.txt", "r", stdin);
// freopen("out.txt", "w", stdout);
// #endif
}
const ll mod = 1e9 + 7, maxn = 1e6 + 5, maxm = 20, inf = ll(1e9) + 5;
int val[maxn], ed[maxm], nxt[maxm], tmp;
vector<pp> adj[maxn];
void dfs(int r, int p, int v){
val[r] = v;
for(auto[c, w]: adj[r]) if(c - p){
if(w + 1){
ed[tmp] = r;
nxt[tmp] = w;
tmp++;
dfs(c, r, v|(1<<(tmp-1)));
} else{
dfs(c, r, v);
}
}
}
int dist[maxm + 5][maxn];
void dfs2(int r, int p, int id){
for(auto[c, w]: adj[r]) if(c - p){
dist[id][c] = dist[id][r] + 1;
dfs2(c, r, id);
}
}
int dp[1<<maxm][maxm];
int main(){ IOS();
int n, s, t; cin >> n >> s >> t; s--, t--;
int m = 0;
rep(i,1,n){
int u, v, w; cin >> u >> v >> w; u--, v--, w--;
adj[u].pb({v, w});
adj[v].pb({u, w});
m += w != -1;
}
dfs(s, -1, 0);
rep(i,0,m){
dfs2(ed[i], -1, i);
}
dfs2(s, -1, m);
auto chk = [&](int msk, int r){
return (val[r]&msk) == val[r];
};
per(i,(1<<m)-1,1){
vector<int> is, nis;
is.reserve(m);
nis.reserve(m);
rep(e,0,m) {
if(i>>e&1){
if(chk(i, ed[e])) is.pb(e);
}else{
if(chk(i, nxt[e]) && chk(i, ed[e])) nis.pb(e);
}
}
for(int e: is){
dp[i][e] = inf;
if(chk(i, t)){
dp[i][e] = dist[e][t];
}else{
for(int x: nis){
dp[i][e] = min(dp[i][e], dp[i^(1<<x)][x] + dist[e][nxt[x]] + dist[x][nxt[x]]);
}
}
}
}
int ans = inf;
rep(i,0,m){
if(chk(0, nxt[i]) && chk(0, ed[i])) ans = min(ans, dp[1<<i][i] + dist[m][nxt[i]] + dist[i][nxt[i]]);
}
if(chk(0, t)){
ans = dist[m][t];
}
cout << (ans == inf? -1: ans) << '\n';
return 0;
}
