#include <bits/stdc++.h>
using namespace std;
#define __Master_Moon__ int main()
#define ll long long
#define el "\n"
#define fi first
#define sq(x) (x)*(x)
#define se second
#define pub push_back
#define puf push_front
#define pii pair <int, int>
#define pll pair <long long, long long>
#define piii pair <int, pair <int, int>>
#define iiii pair <int, pair <int, pair <int, int>>>
#define plll pair <long long, pair <long long, long long>>
#define FOR(i, a, b) for(int i = (a);i <=(b);i++)
#define FO(i, a, b) for(int i = (a);i >= (b);i--)
#define REP(i, n) for(int i = 0;i < (n);i++)
long const maxn = 1e6 + 5;
long const lg = 21;
long const MASK = (1 << 20) + 2;
int dp[21][MASK][2],p[maxn][lg],OR[maxn][lg],it;
int dist[100][100],res[100][100],id[maxn],a[100];
int s,t,n,h[maxn],val[21],vertical[21][2],lca;
int ans = INT_MAX,m = 0;
vector<pii> g[maxn];
void dfs(int u,int par)
{
h[u] = h[par] + 1;
for(pii x : g[u])
{
if(x.fi != par)
{
p[x.fi][0] = u;
OR[x.fi][0] = x.se;
dfs(x.fi,u);
}
}
}
void init()
{
FOR(i,1,20)
{
FOR(j,1,n)
{
p[j][i] = p[p[j][i-1]][i-1];
OR[j][i] = OR[j][i-1] | OR[p[j][i-1]][i-1];
}
}
}
int LCA(int u,int v)
{
if(h[u] < h[v]) swap(u,v);
int tmp = h[u] - h[v],res = 0;
FO(i,20,0)
{
if(tmp >= (1<<i))
{
tmp -= (1<<i);
res = res | OR[u][i];
u = p[u][i];
}
}
if(u == v)
{
lca = u;
return res;
}
FO(i,20,0)
{
if(p[u][i] != p[v][i])
{
res = res | OR[u][i] | OR[v][i];
u = p[u][i];
v = p[v][i];
}
}
res = res | OR[u][0] | OR[v][0];
lca = p[u][0];
return res;
}
void compress()
{
FOR(i,1,m) id[a[i]] = i;
FOR(i,1,m)
{
FOR(j,1,m)
{
res[i][j] = LCA(a[i],a[j]);
dist[i][j] = h[a[i]] + h[a[j]] - 2*h[lca];
}
}
}
int build(int start,int to,int between,int key,int mask)
{
int tmp = 0;
start = id[start];
to = id[to];
between = id[between];
if((res[start][between] | mask) != mask) return -1;
tmp += dist[start][between];
mask |= (1<<key);
if((res[to][between] | mask) != mask) return -1;
tmp += dist[to][between];
return tmp;
}
void solve()
{
cin >> n >> s >> t;
memset(dp,-1,sizeof dp);
FOR(i,1,n-1)
{
int u,v,w,tmp = 0;
cin >> u >> v >> w;
if(w)
{
tmp = (1<<it);
val[it] = w;
vertical[it][0] = u;
vertical[it][1] = v;
if(id[u] == 0) {m++; a[m] = u;}
if(id[v] == 0) {m++; a[m] = v;}
if(id[w] == 0) {m++; a[m] = w;}
id[u] = id[v] = id[w] = 1;
it++;
}
g[u].pub({v,tmp});
g[v].pub({u,tmp});
}
dfs(1,0);
init();
if(LCA(s,t) == 0)
{
cout << h[s] + h[t] - 2*h[lca];
return;
}
if(id[s] == 0) {m++; a[m] = s;}
if(id[t] == 0) {m++; a[m] = t;}
compress();
REP(i,it)
{
int u = vertical[i][0],v = vertical[i][1];
dp[i][(1<<i)][0] = build(s,u,val[i],i,0);
dp[i][(1<<i)][1] = build(s,v,val[i],i,0);
}
REP(mask,(1<<it))
{
if(__builtin_popcount(mask) <= 1) continue;
REP(i,it)
{
if(mask&(1<<i))
{
REP(j,it)
{
if(j != i && mask&(1<<j))
{
if(dp[j][mask^(1<<i)][1] != -1)
{
int tmp = build(vertical[j][1],vertical[i][0],val[i],i,mask^(1<<i));
int mtp = build(vertical[j][1],vertical[i][1],val[i],i,mask^(1<<i));
if(tmp != -1)
{
tmp += dp[j][mask^(1<<i)][1];
if(dp[i][mask][0] == -1) dp[i][mask][0] = tmp;
else dp[i][mask][0] = min(dp[i][mask][0],tmp);
}
if(mtp != -1)
{
mtp += dp[j][mask^(1<<i)][1];
if(dp[i][mask][1] == -1) dp[i][mask][1] = mtp;
else dp[i][mask][1] = min(dp[i][mask][1],mtp);
}
}
if(dp[j][mask^(1<<i)][0] != -1)
{
int tmp = build(vertical[j][0],vertical[i][0],val[i],i,mask^(1<<i));
int mtp = build(vertical[j][0],vertical[i][1],val[i],i,mask^(1<<i));
if(tmp != -1)
{
tmp += dp[j][mask^(1<<i)][0];
if(dp[i][mask][0] == -1) dp[i][mask][0] = tmp;
else dp[i][mask][0] = min(dp[i][mask][0],tmp);
}
if(mtp != -1)
{
mtp += dp[j][mask^(1<<i)][0];
if(dp[i][mask][1] == -1) dp[i][mask][1] = mtp;
else dp[i][mask][1] = min(dp[i][mask][1],mtp);
}
}
}
}
if(dp[i][mask][0] != -1 && (res[id[vertical[i][0]]][id[t]] | mask) == mask)
ans = min(ans,dp[i][mask][0] + dist[id[vertical[i][0]]][id[t]]);
if(dp[i][mask][1] != -1 && (res[id[vertical[i][1]]][id[t]] | mask) == mask)
ans = min(ans,dp[i][mask][1] + dist[id[vertical[i][1]]][id[t]]);
}
}
}
if(ans == INT_MAX) ans = -1;
cout << ans;
}
__Master_Moon__
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
