#include <bits/stdc++.h>
using namespace std;
#define int long long
#define inf 0x3F3F3F3F3F3F3F3F
struct DSU
{
vector<int> e;
void init(int n)
{
e.assign(n + 1, -1);
}
int get(int x)
{
if (e[x] < 0) return x;
return e[x] = get(e[x]);
}
void unite(int x, int y)
{
x = get(x), y = get(y);
if (x == y) return;
if (e[x] > e[y]) swap(x, y);
e[x] += e[y];
e[y] = x;
}
};
const int MXN = 1e6 + 5;
const int LOG = 20;
int n, S, T;
vector<array<int, 2>> adj[MXN];
int p[LOG][MXN], dep[MXN], in[MXN], out[MXN], tim;
int b[MXN], need[MXN];
int dp[20][(1LL << 20)];
vector<array<int, 3>> m;
void dfs(int a)
{
in[a] = ++tim;
for (array<int, 2> &v : adj[a])
{
if (v[0] == p[0][a]) continue;
p[0][v[0]] = a;
dep[v[0]] = dep[a] + 1;
need[v[0]] = need[a];
if (v[1])
{
int ind = lower_bound(m.begin(), m.end(), array<int, 3> {a, v[0], v[1]}) - m.begin();
need[v[0]] = need[a] | (1LL << ind);
}
dfs(v[0]);
}
out[a] = tim;
}
int anc(int u, int v)
{
return in[u] <= in[v] && out[v] <= out[u];
}
int LCA(int u, int v)
{
if (anc(u, v)) return u;
if (anc(v, u)) return v;
for (int i = LOG - 1; i >= 0; i--)
{
if (anc(p[i][u], v)) continue;
u = p[i][u];
}
return p[0][u];
}
int DIST(int u, int v)
{
return dep[u] + dep[v] - 2 * dep[LCA(u, v)];
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cin >> n >> S >> T;
DSU dsu;
dsu.init(n);
for (int i = 1; i < n; i++)
{
int u, v, w;
cin >> u >> v >> w;
adj[u].push_back({v, w});
adj[v].push_back({u, w});
if (w) m.push_back({u, v, w});
if (!w) dsu.unite(u, v);
}
sort(m.begin(), m.end());
p[0][S] = S;
dfs(S);
for (array<int, 3> &i : m) if (p[0][i[0]] == i[1]) swap(i[0], i[1]);
dfs(S);
for (int i = 1; i < LOG; i++) for (int j = 1; j <= n; j++) p[i][j] = p[i - 1][p[i - 1][j]];
for (int i = 0; i < m.size(); i++) for (int j = 0; j < (1LL << (int)m.size()); j++) dp[i][j] = inf;
for (int i = 0; i < m.size(); i++)
{
b[i] = (need[m[i][0]] ^ need[m[i][2]] ^ need[LCA(m[i][0], m[i][2])]);
}
if (dsu.get(S) == dsu.get(T))
{
cout << DIST(S, T) << '\n';
return 0;
}
for (int msk = 1; msk < (1LL << (int)(m.size())); msk++)
{
if (__builtin_popcount(msk) == 1)
for (int i = 0; i < m.size(); i++)
{
if (!b[i] && (msk >> i & 1))
{
dp[i][msk] = DIST(S, m[i][2]) + DIST(m[i][2], m[i][0]);
}
}
for (int i = 0; i < m.size(); i++)
{
if (dp[i][msk] >= inf) continue;
for (int j = 0; j < m.size(); j++)
{
if ((msk >> j & 1)) continue;
if (((msk ^ b[j]) & b[j])) continue;
dp[j][msk | (1LL << j)] = min(dp[j][msk | (1LL << j)], dp[i][msk] + DIST(m[i][0], m[j][2]) + DIST(m[j][2], m[j][0]));
}
}
}
int res = inf;
for (int msk = 1; msk < (1LL << (int)m.size()); msk++)
{
for (int i = 0; i < m.size(); i++)
{
if (dp[i][msk] >= inf) continue;
if (((msk ^ need[T]) & need[T])) continue;
res = min(res, dp[i][msk] + DIST(m[i][0], T));
}
}
cout << (res >= inf ? -1 : res) << '\n';
}
