// In the name of the God
#include <bits/stdc++.h>
#define ll long long
#define int long long
#define pb push_back
#define F first
#define S second
#define mp make_pair
#define pii pair <int, int>
#define smin(x, y) (x) = min((x), (y))
#define smax(x, y) (x) = max((x), (y))
#define all(x) (x).begin(), (x).end()
using namespace std;
//#pragma GCC optimize("O3,unroll-loops")
//#pragma GCC target("avx2")
const int inf = 1e9+7;
const int mod = 998244353;
const int maxn = 1e6+5, lg = 22;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n, m, s, t, ti = 0, h[maxn], in[maxn], out[maxn], par[maxn][lg], dist[lg][lg], ne[lg][lg], dp[1<<lg][lg];
vector <int> adj[maxn];
vector <pair <pii, int>> g;
void dfs(int v, int p) {
par[v][0] = p;
for (int i = 1; i < lg; i++) par[v][i] = par[par[v][i-1]][i-1];
in[v] = ti++;
for (int u : adj[v]) {
if (u == p) continue;
h[u] = h[v]+1;
dfs(u, v);
}
out[v] = ti;
}
int lca(int v, int u) {
if (h[v] < h[u]) swap(v, u);
int x = h[v]-h[u];
for (int i = 0; i < lg; i++) {
if (x&(1<<i)) v = par[v][i];
}
if (v == u) return v;
for (int i = lg-1; i >= 0; i--) {
if (par[v][i] != par[u][i]) v = par[v][i], u = par[u][i];
}
return par[v][0];
}
int d(int v, int u) {
int z = lca(u, v);
return h[v]+h[u]-h[z]*2;
}
bool isd(int v, int u) {
return in[v] <= in[u] and out[v] >= out[u];
}
int f(int v, int u) {
int res = 0, z = lca(u, v);
for (int i = 0; i < m; i++) {
int x = g[i].F.F, y = g[i].F.S;
bool f = 0;
f = (isd(y, v)&isd(z, x))|(isd(y, u)&isd(z, x));
if (f) res += 1<<i;
}
return res;
}
int32_t main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> s >> t; s--, t--;
for (int i = 1; i < n; i++) {
int v, u, w; cin >> v >> u >> w; v--, u--, w--;
adj[v].pb(u), adj[u].pb(v);
if (w != -1) g.pb(mp(mp(v, u), w));
}
m = g.size();
dfs(s, s);
for (auto &p : g) if (h[p.F.F] > h[p.F.S]) swap(p.F.F, p.F.S);
for (int i = 0; i < m; i++) {
for (int j = 0; j < m; j++) {
dist[i][j] = d(g[i].F.F, g[j].S);
ne[i][j] = f(g[i].F.F, g[j].S);
}
}
for (int i = 0; i < (1<<m); i++) {
for (int j = 0; j < m; j++) dp[i][j] = inf*inf;
}
for (int i = 0; i < m; i++) {
if (f(s, g[i].S) == 0 and f(g[i].S , g[i].F.F) == 0) dp[1<<i][i] = d(s, g[i].S)+d(g[i].S, g[i].F.F);
}
for (int i = 0; i < (1<<m); i++) {
for (int j = 0; j < m; j++) {
if (i&(1<<j)) {
for (int k = 0; k < m; k++) {
if (!(i&(1<<k))) {
if ((ne[j][k]|i) == i and (ne[k][k]|i) == i) smin(dp[i+(1<<k)][k], dp[i][j]+dist[j][k]+dist[k][k]);
}
}
}
}
}
if (s == t) return cout << 0 << '\n', 0;
int ali = -1, p = t;
while (p != s) {
for (int i = 0; i < m; i++) {
if (g[i].F.S == p) {
ali = i;
goto TH;
}
}
p = par[p][0];
}
TH:;
if (ali == -1) return cout << d(s, t) << '\n', 0;
int amir = d(g[ali].F.F, t), ans = inf*inf;
for (int i = 0; i < (1<<m); i++) smin(ans, amir+dp[i][ali]);
cout << (ans == inf*inf ? -1 : ans) << '\n';
return 0;
}
/*
srand(time(0));
cout << (rand()%1900) + 1 << ' ' << (rand()%2)+5 << '\n';
*/
