#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef unsigned long long ull;
//typedef __uint128_t L;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
cerr << " " << H;
debug_out(T...);
}
#define debug(...) cerr << "(" << #__VA_ARGS__ << "):", debug_out(__VA_ARGS__)
#define all(x) x.begin(), x.end()
#define MP(x, y) make_pair(x, y)
#define F first
#define S second
const int maxn = 1e6 + 10;
const int maxm = 20;
const int mask = (1 << 20);
const int inf = 1e9;
int n, m, S, T, edge[maxm][3], comp[maxn], cnt, sz, par[mask][maxm+1], h[maxm+1][maxn], dp[mask][maxm+1];
vector<int> g[maxn];
bool vis[maxn];
int first[maxn], to[maxn << 1], nxt[maxn << 1], ecnt;
void add(int u, int v){
nxt[++ecnt] = first[u];
to[ecnt] = v;
first[u] = ecnt;
}
void dfs(int v, int *h, int p = -1){
for (int i = first[v]; i; i = nxt[i]){
int u = to[i];
if (u != p){
h[u] = h[v] + 1;
dfs(u, h, v);
}
}
}
void getcomp(int v, int p = -1){
vis[v] = true;
comp[v] = cnt;
for (auto u: g[v]) if (u != p) getcomp(u, v);
}
int getpar(int *par, int v){
//debug(v, par[v]);
return (par[v] < 0? v: par[v] = getpar(par, par[v]));
}
void merge(int *par, int u, int v){
if ((u = getpar(par, u)) == (v = getpar(par, v))) return;
if (par[u] > par[v]) swap(u, v);
par[u] += par[v];
par[v] = u;
}
int main(){
// ios_base::sync_with_stdio(false); cin.tie(0);
scanf("%d%d%d", &n, &S, &T);
for (int i = 1; i < n; i++){
int u, v, w; scanf("%d%d%d", &u, &v, &w);
add(u, v);
add(v, u);
if (w == 0){
g[u].push_back(v);
g[v].push_back(u);
}
else{
edge[m][0] = u;
edge[m][1] = v;
edge[m][2] = w;
m++;
}
}
dfs(S, h[m]);
for (int i = 0; i < m; i++){
if (h[m][edge[i][0]] > h[m][edge[i][1]]) swap(edge[i][0], edge[i][1]);
dfs(edge[i][0], h[i]);
}
assert(m <= 20);
for (int i = 1; i <= n; i++){
if (!vis[i]){
getcomp(i);
cnt++;
}
}
for (int i = (1 << m) - 1; ~i; i--){
if (i == (1 << m) - 1){
for (int j = 0; j <= m; j++) par[i][j] = -1;
continue;
}
int tmp = __builtin_ctz(((1 << m) - 1) ^ i);
for (int j = 0; j <= m; j++){
par[i][j] = par[i^(1 << tmp)][j];
}
merge(par[i], comp[edge[tmp][0]], comp[edge[tmp][1]]);
}
for (int i = 0; i <= m; i++){
dp[0][i] = h[i][T];
}
for (int msk = 1; msk < (1 << m); msk++){
for (int i = 0; i <= m; i++){
int v = (i == m? S: edge[i][0]);
dp[msk][i] = inf;
if (getpar(par[msk], comp[T]) == getpar(par[msk], comp[v])){
dp[msk][i] = h[i][T];
continue;
}
for (int tmp = msk; tmp; tmp ^= tmp & -tmp){
int j = __builtin_ctz(tmp);
if (getpar(par[msk], comp[edge[j][2]]) == getpar(par[msk], comp[v]) &&
getpar(par[msk], comp[edge[j][0]]) == getpar(par[msk], comp[v])){
dp[msk][i] = min(dp[msk][i], dp[msk^(1 << j)][j] + h[i][edge[j][2]] + h[j][edge[j][2]]);
}
}
}
}
if (dp[(1 << m) - 1][m] == inf) printf("%d\n", -1);
else printf("%d\n", dp[(1 << m) - 1][m]);
return 0;
}
