#include <bits/stdc++.h>
using namespace std;
const int hx=2e3+5, nx=2e5+5, inf=1e9, kx=19;
int n, m, p, qrs, u, v, x[nx], y[nx], mn[hx][hx], nd[hx][hx], dx[4]={1, 0, 0, -1}, dy[4]={0, 1, -1, 0}, l[2*nx], r[2*nx], t, pa[2*nx][kx], lvl[2*nx], vl[2*nx], dsu[2*nx];
char mp[hx][hx];
vector<tuple<int, int, int>> edg;
queue<pair<int, int>> q;
int find(int x)
{
if (dsu[x]==x) return x;
return dsu[x]=find(dsu[x]);
}
void dfs(int u, int p)
{
lvl[u]=lvl[p]+1;
pa[u][0]=p;
for (int i=1; i<kx; i++) pa[u][i]=pa[pa[u][i-1]][i-1];
if (l[u]) dfs(l[u], u);
if (r[u]) dfs(r[u], u);
}
int lca(int u, int v)
{
if (lvl[u]>lvl[v]) swap(u, v);
for (int i=kx-1; i>=0; i--) if (lvl[pa[v][i]]>=lvl[u]) v=pa[v][i];
if (u==v) return u;
for (int i=kx-1; i>=0; i--) if (pa[u][i]!=pa[v][i]) u=pa[u][i], v=pa[v][i];
return pa[u][0];
}
int main()
{
cin.tie(NULL)->sync_with_stdio(false);
cin>>n>>m>>p>>qrs;
for (int i=1; i<=n; i++) for (int j=1; j<=m; j++) cin>>mp[i][j], mn[i][j]=inf;
for (int i=1; i<=p; i++) cin>>x[i]>>y[i], nd[x[i]][y[i]]=i, mn[x[i]][y[i]]=0, q.push({x[i], y[i]});
while (!q.empty())
{
auto [cx, cy]=q.front();
q.pop();
for (int dir=0; dir<4; dir++)
{
int newx=cx+dx[dir], newy=cy+dy[dir];
if (mp[newx][newy]=='.'&&!nd[newx][newy])
{
mn[newx][newy]=mn[cx][cy]+1;
nd[newx][newy]=nd[cx][cy];
q.push({newx, newy});
}
}
}
for (int i=1; i<=n; i++) for (int j=1; j<m; j++) if (mp[i][j]=='.'&&mp[i][j+1]=='.'&&nd[i][j]) edg.push_back({mn[i][j]+mn[i][j+1], nd[i][j], nd[i][j+1]});
for (int i=1; i<n; i++) for (int j=1; j<=m; j++) if (mp[i][j]=='.'&&mp[i+1][j]=='.'&&nd[i][j]) edg.push_back({mn[i][j]+mn[i+1][j], nd[i][j], nd[i+1][j]});
for (int i=1; i<p; i++) edg.push_back({inf, i, i+1});
sort(edg.begin(), edg.end());
for (int i=1; i<=2*p; i++) dsu[i]=i;
t=p;
for (auto [w, u, v]:edg)
{
if (find(u)!=find(v))
{
t++;
l[t]=find(u), r[t]=find(v), vl[t]=w;
dsu[find(u)]=dsu[find(v)]=t;
}
}
dfs(t, t);
while (qrs--) cin>>u>>v, cout<<vl[lca(u, v)]<<'\n';
}
