#include <bits/stdc++.h>
//code
#define fl(i,x,y,z) for(int i=x;i<=y;i=i+z)
#define fn(i,x,y,z) for(int i=x;i>=y;i=i-z)
#define rep(i,x,y) for(int i=x;i<y;i=i+1)
#define all(v) v.begin(),v.end()
#define pb emplace_back
#define tle cout<<"tle"<<endl
#define edl cout<<"\n"
#define el "\n"
#define getbit(x,i) ((x>>i)&1)
#define bitcnt __builtin_popcount
//ham
//#define pii pair<int,int>
#define fi first
#define se second
#define ll long long
#define ld long double
using namespace std;
const int N = int(5e5) + 7;
const int inf = 1e9 + 1;
typedef pair<ll, ll> pii;
int n, m, k, d[N], p, u, v, w;
vector<pii> e[N];
struct TEdges {
int u, v, w;
TEdges() {u = v = w = 0;}
TEdges(int u, int v, int w): u(u), v(v), w(w) {}
bool operator < (const TEdges& x)const& {
return w > x.w;
}
};
vector<TEdges> edges;
priority_queue<pii, vector<pii>, greater<pii>> q;
int lab[N],sz[N];
int findset(int u)
{
if (lab[u]==u) return u;
return lab[u]=findset(lab[u]);
}
bool joinset(int u,int v)
{
u=findset(u),v=findset(v);
if (u==v) return false;
if (sz[u]<sz[v]) swap(u,v);
lab[v]=u;
sz[u]+=sz[v];
return true;
}
const int logN = 20;
int f[N][logN + 1], g[N][logN + 1], h[N];
void DFS(int u)
{
for (auto it: e[u])
{
int v=it.fi,c=it.se;
if (v==f[u][0]) continue;
h[v]=h[u]+1;
f[v][0]=u;
g[v][0]=c;
fl(i,1,18,1)
{
f[v][i]=f[f[v][i-1]][i-1];
g[v][i]=min(g[v][i-1],g[f[v][i-1]][i-1]);
}
DFS(v);
}
}
int lca(int u, int v) {
if (h[u]<h[v]) swap(u,v);
int res=inf;
int k=h[u]-h[v];
fn(i,17,0,1)
if (getbit(k,i))
{
res=min(res,g[u][i]);
u=f[u][i];
}
if (u==v) return res;
fn(i,17,0,1)
if (f[u][i]!=f[v][i])
{
res=min(res,g[u][i]);
res=min(res,g[v][i]);
u=f[u][i],v=f[v][i];
}
res=min(res,g[u][0]);
res=min(res,g[v][0]);
return res;
}
void inp()
{
cin >> n >> m>>k>>p;
fl(i,1,m,1)
{
int u,v,w; cin>>u>>v>>w;
e[u].pb(v,w);
e[v].pb(u,w);
edges.pb(u,v,w);
}
fill_n(&g[0][0], N * (logN + 1), inf);
fl(i,1,n,1)
{
lab[i]=i;
sz[i]=1;
}
fill(d, d + n + 1, inf);
fl(i,1,k,1)
{
cin >> u;
d[u] = 0, q.emplace(d[u], u);
}
}
void sol()
{
pii top;
while(q.size()) {
top = q.top(); q.pop();
if(top.fi != d[top.se]) continue;
for(auto& v: e[top.se]) {
if(top.fi + v.se < d[v.fi]) {
d[v.fi] = top.fi + v.se;
q.emplace(d[v.fi], v.fi);
}
}
}
for(auto& it: edges) it.w = min(d[it.u], d[it.v]);
sort(edges.begin(), edges.end());
fl(i,1,n,1) e[i].clear();
for(auto &it: edges) {
if(joinset(it.u, it.v)) {
e[it.u].pb(it.v, it.w);
e[it.v].pb(it.u, it.w);
}
}
DFS(1);
while(p --) {
cin >> u >> v;
cout << lca(u, v) << '\n';
}
}
signed main()
{
#define name "walk"
if (fopen(name".inp", "r"))
{
freopen(name".inp", "r", stdin);
freopen(name". Out", "w", stdout);
}
ios_base::sync_with_stdio(false);
cin.tie(NULL);
inp();
sol();
return 0;
}
