// Alir3za.Zar3 -> Shiraz , Iran
#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
//#define int long long
const int maxn = 1e6+7 , maxm = 21;
const int inF = 1e9;
int n,s,t,q , dp[maxm][1<<maxm],p[maxm][maxn];
int len[maxm][maxm] , qmsk[maxn] , dep[maxn];
int f[maxm] , key[maxm] , door[maxm];
vector<pair<int,int>> e[maxn];
void dfs (int v)
{
for (auto [u , lock] : e[v])
if (u != p[0][v])
{
p[0][u] = v , dep[u] = dep[v]+1;
if (lock)
qmsk[u] = 1<<lock-1 , door[lock-1] = v;
qmsk[u] |= qmsk[v];
dfs(u);
}
}
int lca (int v , int u)
{
if (dep[v] < dep[u]) swap(v , u);
int k = dep[v] - dep[u];
for (int bit=0; bit<maxm; bit++)
if ((1<<bit)&k) v = p[bit][v];
if (v == u) return v;
for (int bit=maxm-1; bit>=0; bit--)
if (p[bit][v] != p[bit][u])
v = p[bit][v] , u = p[bit][u];
return p[0][v];
}
void calc_dp (int v , int msk)
{
if (dp[v][msk] != -1) return;
if (!(msk & qmsk[t]))
{
dp[v][msk] = f[v]; return;
}
dp[v][msk] = inF;
for (int k=0; k<q; k++)
if ((1<<k)&msk)
{
int vmsk = qmsk[key[k]]|qmsk[door[k]];
if (!(vmsk & msk))
calc_dp(k , msk ^ (1<<k)) ,\
dp[v][msk] = min(dp[v][msk] , dp[k][msk^(1<<k)]+len[v][k]);
}
}
signed main ()
{
ios::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
cin >> n >> s >> t;
for (int i=1; i<n; i++)
{
int u,v,k; cin >> u >> v >> k;
if (k) key[q++] = k , k=q;
e[v].push_back({ u , k });
e[u].push_back({ v , k });
}
door[q] = s;
dfs(s); p[0][s] = s;
for (int i=1; i<maxm; i++)
for (int v=1; v<=n; v++)
p[i][v] = p[i-1][p[i-1][v]];
for (int i=0; i<=q; i++)
for (int j=0; j<q; j++)
{
int l0 = lca(door[i] , key[j]);
int l1 = lca(key[j] , door[j]);
len[i][j] = dep[door[i]]+dep[key[j]]*2+dep[door[j]]
- dep[l0]*2 - dep[l1]*2;
}
for (int i=0; i<=q; i++)
{
int l = lca(door[i] , t);
f[i] = dep[door[i]]+dep[t]-dep[l]*2;
}
memset(dp , -1 , sizeof(dp));
calc_dp(q , (1<<q)-1);
if (dp[q][(1<<q)-1] == inF)
cout << -1 << '\n';
else
cout << dp[q][(1<<q)-1] << '\n';
}
