#include <bits/stdc++.h>
using namespace std;
#define mins(a, b) (a = min(a, b))
const int MXN = 1e6+5, MXM = 21, inf = 1e9;
int n, s, t, U[MXN], V[MXN], W[MXN], key[MXM], door[MXM], par[MXM][MXN], h[MXN], dis[MXM][MXM];
int mask[MXN], dp[MXM][1<<MXM], timer, dest[MXM];
vector<int> g[MXN];
void dfs(int v) {
for(int i=1; i<MXM; i++) par[i][v] = par[i-1][par[i-1][v]];
for(int i : g[v]) {
int u = v^U[i]^V[i];
if(u==par[0][v]) continue;
par[0][u] = v;
h[u] = h[v]+1;
mask[u] = mask[v];
if(W[i]!=-1) {
door[W[i]] = v;
mask[u] |= 1<<W[i];
}
dfs(u);
}
}
inline int jump(int v, int d) {
for(int i=0; i<MXM; i++)
if(d>>i&1)
v = par[i][v];
return v;
}
inline int LCA(int u, int v) {
if(h[u]<h[v]) swap(u, v);
u = jump(u, h[u]-h[v]);
if(u==v) return u;
for(int i=MXM-1; i>=0; i--)
if(par[i][u]!=par[i][v])
u = par[i][u], v = par[i][v];
return par[0][u];
}
void DP(int v, int msk) {
if(dp[v][msk] != -1) return;
if(!(mask[t] & msk)) {
dp[v][msk] = dest[v];
return;
}
dp[v][msk] = inf;
for(int i=0; i<timer; i++) if(msk>>i&1)
if(!((mask[key[i]]|mask[door[i]]) & msk)) {
DP(i, msk^(1<<i));
mins(dp[v][msk], dp[i][msk^(1<<i)] + dis[v][i]);
}
}
int32_t main() {
cin.tie(0); cout.tie(0); ios_base::sync_with_stdio(0);
cin >> n >> s >> t;
for(int i=0; i<n-1; i++) {
cin >> U[i] >> V[i] >> W[i];
if(W[i]==0) W[i] = -1;
else key[W[i]=timer++] = W[i];
g[U[i]].push_back(i);
g[V[i]].push_back(i);
}
door[timer] = s;
dfs(s);
for(int i=0; i<=timer; i++) {
for(int j=0; j<timer; j++) if(i^j)
dis[i][j] = h[door[i]] + 2*h[key[j]] + h[door[j]]
- 2*h[LCA(door[i], key[j])] - 2*h[LCA(key[j], door[j])];
dest[i] = h[door[i]] + h[t] - 2*h[LCA(door[i], t)];
}
memset(dp, -1, sizeof(dp));
DP(timer, (1<<timer)-1);
cout << (dp[timer][(1<<timer)-1]==inf ? -1 : dp[timer][(1<<timer)-1]) << '\n';
return 0;
}
