#pragma GCC optimize("Ofast,unroll-loops")
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define F first
#define S second
using namespace std;
const ll INF = 1e17;
ll N, Sh, Q, E, head[20][100005], dis[20][100005], seg[20][400005], echild[20][100005], t[20], vis[100005], sz[100005], dfsorder[20][100005];
pii io[20][100005];
bool isshop[100005], hide[20][400005];
vector<pair<int, pll>> edge[100005];
void dfs_sz(int k, int layer)
{
vis[k] = 1;
sz[k] = 1;
for (auto p : edge[k])
if (!vis[p.F])
{
dfs_sz(p.F, layer);
sz[k] += sz[p.F];
}
vis[k] = 0;
}
int dfs_find_cent(int k, int layer, int root)
{
vis[k] = 1;
bool valid = true;
for (auto p : edge[k])
if (!vis[p.F])
{
int cent = dfs_find_cent(p.F, layer, root);
if (cent)
{
vis[k] = 0;
return cent;
}
if (sz[p.F] > sz[root] / 2)
valid = false;
}
vis[k] = 0;
if (valid && sz[root] - sz[k] <= sz[root] / 2)
return k;
return 0;
}
void dfs_init(int k, int layer, int root)
{
vis[k] = 1;
io[layer][k].F = ++t[layer];
dfsorder[layer][io[layer][k].F] = k;
head[layer][k] = root;
for (auto p : edge[k])
if (!vis[p.F])
{
dis[layer][p.F] = dis[layer][k] + p.S.S;
echild[layer][p.S.F] = p.F;
dfs_init(p.F, layer, root);
}
vis[k] = 0;
io[layer][k].S = t[layer];
}
void cent_dec(int root, int layer)
{
assert(layer <= 18);
dfs_sz(root, layer);
int cent = dfs_find_cent(root, layer, root);
dfs_init(cent, layer, cent);
vis[cent] = 1;
for (auto p : edge[cent])
if (!vis[p.F])
cent_dec(p.F, layer + 1);
}
void build(int layer, int i = 1, int L = 1, int R = N)
{
if (L == R)
{
int u = dfsorder[layer][L];
if (isshop[u])
seg[layer][i] = dis[layer][u];
else
seg[layer][i] = INF;
}
else
{
int mid = (L + R) / 2;
build(layer, i * 2, L, mid);
build(layer, i * 2 + 1, mid + 1, R);
seg[layer][i] = min(seg[layer][i * 2], seg[layer][i * 2 + 1]);
}
}
ll getval(int layer, int i)
{
if (hide[layer][i])
return INF;
else
return seg[layer][i];
}
void modify(int layer, int mL, int mR, bool val, int i = 1, int L = 1, int R = N)
{
if (mL <= L && R <= mR)
hide[layer][i] = val;
else if (mR < L || R < mL)
return;
else
{
int mid = (L + R) / 2;
modify(layer, mL, mR, val, i * 2, L, mid);
modify(layer, mL, mR, val, i * 2 + 1, mid + 1, R);
seg[layer][i] = min(getval(layer, i * 2), getval(layer, i * 2 + 1));
}
}
ll query(int layer, int qL, int qR, int i = 1, int L = 1, int R = N)
{
if (qL <= L && R <= qR)
return getval(layer, i);
else if (qR < L || R < qL)
return INF;
else
{
int mid = (L + R) / 2;
return min(query(layer, qL, qR, i * 2, L, mid),
query(layer, qL, qR, i * 2 + 1, mid + 1, R));
}
}
signed main()
{
ios::sync_with_stdio(0), cin.tie(0);
cin >> N >> Sh >> Q >> E;
assert(Q <= 100000);
for (int i = 1; i < N; i++)
{
int A, B, W;
cin >> A >> B >> W;
edge[A].emplace_back(make_pair(B, pll{i, W}));
edge[B].emplace_back(make_pair(A, pll{i, W}));
}
for (int i = 1; i <= Sh; i++)
{
int u;
cin >> u;
isshop[u] = 1;
}
cent_dec(1, 0);
for (int i = 0; i < 20; i++)
dis[i][E] = -INF;
isshop[E] = 1;
for (int i = 0; i < 20; i++)
build(i);
for (int i = 1; i <= Q; i++)
{
ll ans = INF, I, R;
cin >> I >> R;
for (int l = 0; l < 20; l++)
if (head[l][R])
{
int snow = echild[l][I];
if (!(io[l][snow].F <= io[l][R].F && io[l][R].S <= io[l][snow].S))
{
modify(l, io[l][snow].F, io[l][snow].S, 1);
ans = min(ans, dis[l][R] + query(l, io[l][head[l][R]].F, io[l][head[l][R]].S));
modify(l, io[l][snow].F, io[l][snow].S, 0);
//cout << ans << " ";
}
}
if (ans < 0)
cout << "escaped\n";
else if (ans >= 1e15)
cout << "oo\n";
else
cout << ans << '\n';
}
}
