// nhan xet quan trong cho bai nay:
//co the thay m =20 da goi y bai nay la dp bitmask, van de o day la co toi n dinh can luu trang thai
//mot cach giam so luong trang thai hieu qua do la loai bo cac trang thai khong quan trong
//noi cach khac, voi moi canh bi cam ta chi can quan tam va danh dau cac dinh dau mut cua canh nay
//
//No la ki thuat khong cu, co dieu da bi lang quen
//
//Ngoai ra ta co 1 chung minh bo tro nhu sau
//vi no la cay, nen chi ton tai duy nhat 1 duong di tu u den v -> cac duong di kieu gi thi kieu cung di qua dong nay
//
//suy ra voi cac bai mo khoa -> phai lay chia truoc roi tu chia di den o khoa
//ngoai ra nho no la cay ta cung co the de dang kiem tra xem doan duong bat buoc phai qua nhung loai khoa nao
//Het roi!
//
//A mot nhan xet lam giam so chieu
//tu s ta chi di den dinh gan hon (no khong dung voi moi trang thai dp nhung se dung voi ket qua toi uu)
#include <bits/stdc++.h>
#define int long long
#define pii pair<int, int>
#define fi first
#define se second
#define vi vector <int>
#define pq priority_queue
#define MASK(i) (1ll<<(i))
#define BIT(x, i) (((x) >> (i)) & 1)
#define x0 ___x0
#define y0 ___y0
#define div ___div
#define next ___next
#define prev ___prev
#define left ___left
#define right ___right
#define pos pisosi
#define pb push_back
#define pf push_front
using namespace std;
//const int mod = ;
//void add (int &a, const int&b){
// a+=b;
// if (a>=mod) a-=mod;
//}
//
//void sub (int&a, const int&b){
// a-=b;
// if (a<0) a+=mod;
//}
//
//void mul (int&a, const int&b){
// a*=b;
// a%=mod;
//}
template<class X, class Y>
bool minimize(X &x, const Y&y){
if (x<=y) return false;
else{
x = y;
return true;
}
}
template<class X, class Y>
bool maximize (X &x, const Y&y){
if (x>=y) return false;
else{
x = y;
return true;
}
}
/////////////////////////////////////////////////////////////////////////////////
//// dang nhap ham
//#ifndef davele
//
//#endif // davele
//
//// chay thu ham main:
//
//#ifdef davele
//
//#endif // davele
////////////////////////////////////////////////////////////////////////////
//const int lim = , limit = , inf = ;
const string name = "treemaze";
const int lim = 1100000, limit = lim+5, inf = 1e18;
int n, m, s, t;
int key[limit];
pii edge[limit];
int maskval[limit];
vector <pii> adj[limit];
int pos[limit], numlca, dslca[2*limit];
int rmq[2*limit][21];
int dp[limit][21];
int st[limit], en[limit], cntdfs;
int opt[limit];
int h[limit], summask[limit];
void dfs (int u, int pre){
st[u]=++cntdfs;
pos[u] = ++numlca;
dslca[numlca] = u;
for (pii x:adj[u]){
int v = x.fi, id = x.se;
if (v==pre) continue;
h[v] = h[u]+1;
summask[v] = summask[u] + maskval[id];
dfs(v, u);
dslca[++numlca] = u;
}
en[u] = cntdfs;
}
int getmin (int u, int v){
if (h[u]<h[v]) return u;
return v;
}
int lca (int u, int v){
int l = pos[u], r = pos[v];
if (l>r) swap(l, r);
int tm = 31-__builtin_clz(r-l+1);
return getmin (rmq[l][tm], rmq[r-MASK(tm)+1][tm]);
}
int getbit (int u, int v){
return summask[u]^summask[v];
}
int dist (int u, int v){
int LCA = lca(u, v);
return h[u]+h[v]-2*h[LCA];
}
bool parchild (int pare, int chil){
return (pare&chil)==chil;
}
void process(){
dfs (1, 1);
for (int i=1; i<=numlca; i++) rmq[i][0] = dslca[i];
for (int i=1; i<=20; i++){
for (int j=1; j+MASK(i)-1<=numlca; j++){
rmq[j][i] = getmin (rmq[j][i-1], rmq[j+MASK(i-1)][i-1]);
}
}
for (int i=0; i<m; i++){
int u = edge[i].fi, v = edge[i].se;
if (h[u]<h[v]) swap(u, v);
if (st[s]>=st[u] && st[s]<=en[u]) opt[i] = u;
else opt[i] = v;
}
// xu ly truong hop di mot mach tu s den t
if (getbit(s,t)==0){
cout<<dist(s, t);
return;
}
//
int ALLMASK = MASK(m)-1;
for (int i=1; i<=ALLMASK; i++) for (int j=0; j<m; j++)
dp[i][j] = inf;
// xu ly truong hop 1 bit
for (int i=0; i<m; i++){
int tmp = key[i];
//
if (getbit(s, tmp)==0 && getbit(tmp, opt[i])==0){
minimize (dp[MASK(i)][i], dist(s,tmp)+dist(tmp, opt[i]));
}
// cerr<<getbit(s, tmp)<<"\n";
// cerr<<i<<" "<<tmp<<" "<<fiu<<" "<<seu<<" "<<dp[MASK(i)][i][0]<<" "<<dp[MASK(i)][i][1]<<"\n";
}
int ret = inf;
//
for (int mask=1; mask<=ALLMASK; mask++){
for (int i=0; i<m; i++) if (MASK(i)&mask){
if (dp[mask][i]==inf) continue;
int u = opt[i];
// cerr<<mask<<" "<<i<<" "<<j<<" "<<u<<" "<<dp[mask][i][j]<<"\n";
if (parchild(mask, getbit(u, t))){
// cerr<<u<<" "<<mask<<" "<<dp[mask][i][j]<<" "<<dist(u, t)<<"\n";
minimize (ret, dp[mask][i]+dist(u, t));
}
//
for (int z=0; z<m; z++) if (BIT(mask, z)==0){
int khoa = key[z];
int tmp = getbit(u, khoa);
if (!parchild(mask, tmp)) continue;
int newmask = mask^MASK(z);
if (parchild(mask, getbit(khoa, opt[z]))){
minimize (dp[newmask][z], dp[mask][i]+dist(u, khoa)+dist(khoa, opt[z]));
}
}
}
}
if (ret==inf) cout<<"-1";
else cout<<ret;
}
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
//
// if (fopen((name+".inp").c_str(), "r")){
// freopen ((name+".inp").c_str(), "r", stdin);
// freopen ((name+".out").c_str(), "w", stdout);
// }
//
cin>>n>>s>>t;
m = 0;
for (int i=1; i<n; i++){
int u, v, H;
cin>>u>>v>>H;
if (H>0){
key[m] = H;
edge[m] = {u, v};
maskval[i] = MASK(m);
m++;
}
else{
maskval[i] = 0;
}
adj[u].pb({v, i});
adj[v].pb({u, i});
}
process();
}
