#include <bits/stdc++.h>
#define ll int
#define fi first
#define se second
#define pb push_back
#define ii pair<ll, ll>
#define all(a) a.begin(), a.end()
#define iii pair<ll, ii>
#define ld long double
using namespace std;
const ll N = 1e6+5;
const ll mod = 1e9+7;
const ll inf=1e9+3;
const ll lg =18;
ll n,i,j,m=0,q,k;
ll x,y;
ll s,t,cnt=0;
ll d[23][23],tin[23],tout[23];
ll up[20][N],a[N],par[N],deep[N];
vector<ii>v[N];
bool kt[22][(1<<20)];
bool bit(ll i,ll x)
{
return (x>>i)&1;
}
ll binlift(ll x,ll k)
{
for(ll i=0;i<20;i++)
if((k>>i)&1) x=up[i][x];
return x;
}
ll LCA(ll x,ll y)
{
if(deep[x]<deep[y]) swap(x,y);
x=binlift(x,deep[x]-deep[y]);
if(x==y) return x;
for(ll i=19;i>=0;i--)
{
if(up[i][x]!=up[i][y])
{
x=up[i][x];
y=up[i][y];
}
}
return up[0][x];
}
void dfs(ll u,ll p)
{
up[0][u]=p;
for(ll i=1;i<20;i++)
up[i][u]=up[i-1][up[i-1][u]];
deep[u]=deep[p]+1;
par[u]=p;
for(auto tmp:v[u])
{
ll x=tmp.fi,w=tmp.se;
if(x==p) continue;
a[x]=a[u];
if(w!=0)
{
tin[m]=w;
tout[m]=u;
a[x]|=(1<<m);
m++;
}
dfs(x,u);
}
}
ll dist(ll x,ll y)
{
ll lca=LCA(x,y);
//cout<<x<<" "<<y<<' '<<deep[x]+deep[y]-deep[lca]*2<<'\n';
return deep[x]+deep[y]-deep[lca]*2;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
cin>>n>>s>>t;
if(s==t) return cout<<0,0;
for(i=1;i<n;i++)
{
ll x,y,w;
cin>>x>>y>>w;
v[x].pb({y,w});
v[y].pb({x,w});
}
memset(a,0,sizeof(a));
dfs(s,s);
tin[m]=tout[m]=s;
++m;
tin[m]=tout[m]=t;
for(i=0;i<=m;i++){
for(j=0;j<=m;j++)
if(j!=i)
{
d[i][j]=dist(tout[i],tin[j])+dist(tin[j],tout[j]);
}
d[i][i]=0;
}
priority_queue<iii,vector<iii>,greater<iii>>pq;// dis mask cur
pq.push({0ll,{0ll,m-1}});
ll res=inf;
while(!pq.empty())
{
iii tmp=pq.top();pq.pop();
ll dis=tmp.fi,mask=tmp.se.fi,u=tmp.se.se;
// cout<<u<<" "<<dis<<" "<<mask<<'\n';
if(res<=dis) break;
if(kt[u][mask]) continue;
kt[u][mask]=1;
for(ll i=0;i<m-1;i++)
if(!bit(i,mask)&&(a[tin[i]]&mask)==a[tin[i]]&&(a[tout[i]]&mask)==a[tout[i]]&&!kt[i][mask|(1<<i)])
pq.push({dis+d[u][i],{mask|(1<<i),i}});
if((a[t]&mask)==a[t]) res=min(res,dis+d[u][m]);
}
cout<<(res==inf?-1:res);
return 0;
}
/*
(2^d-1)*(2^k) / (2^n-1)
2^d+k-n - 2^k-n
*/
