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| #include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
#define maxn 200005
#define maxm 4005
#define put() putchar('\n')
#define Tp template<typename Ty>
#define Ts template<typename Ty,typename... Ar>
using namespace std;
inline void read(int &x){
int f=1;x=0;char c=getchar();
while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
while (c>='0'&&c<='9') {x=x*10+c-'0';c=getchar();}
x*=f;
}
namespace Debug{
Tp void _debug(char* f,Ty t){cerr<<f<<'='<<t<<endl;}
Ts void _debug(char* f,Ty x,Ar... y){while(*f!=',') cerr<<*f++;cerr<<'='<<x<<",";_debug(f+1,y...);}
Tp ostream& operator<<(ostream& os,vector<Ty>& V){os<<"[";for(auto& vv:V) os<<vv<<",";os<<"]";return os;}
#define gdb(...) _debug((char*)#__VA_ARGS__,__VA_ARGS__)
}using namespace Debug;
int a[maxm][maxm],n,m,p,T;
int fa[maxn][21],Max[maxn][21],lg[maxn],deep[maxn];
struct zyq{
int to,w;
zyq(int a=0,int b=0) {to=a;w=b;}
};
int ecnt;
vector<zyq>to[200005];
struct node{
int x,y,id;
node (int a=0,int b=0,int c=0) {
x=a;y=b;id=c;
}
}g[maxn];
vector<node>e[4000005];
inline void dfs(int x,int pre,int w) {
int i;deep[x]=deep[pre]+1;fa[x][0]=pre;Max[x][0]=w;
for (i=1;i<=20;i++) {
fa[x][i]=fa[fa[x][i-1]][i-1];
Max[x][i]=max(Max[x][i-1],Max[fa[x][i-1]][i-1]);
}
for (auto tmp:to[x]) if (tmp.to^pre) dfs(tmp.to,x,tmp.w);
}
inline int query(int x,int y) {
int ans=0,i;
if (deep[x]<deep[y]) swap(x,y);
while (deep[x]>deep[y]) ans=max(ans,Max[x][lg[deep[x]-deep[y]]]),x=fa[x][lg[deep[x]-deep[y]]];
if (x==y) return ans;
for (i=lg[deep[x]];i>=0;i--) if (fa[x][i]^fa[y][i]) {
ans=max(ans,max(Max[x][i],Max[y][i]));
x=fa[x][i],y=fa[y][i];
}
return max(ans,max(Max[x][0],Max[y][0]));
}
int fx[5]={0,1,-1,0,0},fy[5]={0,0,0,1,-1};
int vis[maxm][maxm],dis[maxm][maxm];
int father[maxn];
inline int getfa(int x) {return x==father[x]?x:father[x]=getfa(father[x]);}
inline bool cmp(node x,node y) {return x.id<y.id;}
queue<node>q;
signed main(void){
int i,j,k,xx,yy,x,y,z;char ch;
read(n);read(m);read(p);read(T);
for (i=1;i<=n;i++) {
ch=getchar();while (ch!='.'&&ch!='#') ch=getchar();
for (j=1;j<=m;j++) a[i][j]=(ch=='#'),ch=getchar();
}
for (i=2;i<=p;i++) lg[i]=lg[i/2]+1;
for (i=1;i<=p;i++) read(g[i].x),read(g[i].y),g[i].id=i,q.push(node(g[i].x,g[i].y,i)),vis[g[i].x][g[i].y]=i;
for (i=1;i<=p;i++) father[i]=i;
while (!q.empty()) {
auto tmp=q.front();q.pop();
for (i=1;i<=4;i++) {
xx=tmp.x+fx[i];yy=tmp.y+fy[i];
if (xx>=1&&xx<=n&&yy>=1&&yy<=m&&!a[xx][yy]) {
if (vis[xx][yy]) {
x=tmp.id,y=vis[xx][yy];
assert(dis[xx][yy]+dis[tmp.x][tmp.y]<=4000000);
e[dis[xx][yy]+dis[tmp.x][tmp.y]].push_back(node(x,y));
}
else vis[xx][yy]=tmp.id,dis[xx][yy]=dis[tmp.x][tmp.y]+1,q.push(node(xx,yy,tmp.id));
}
}
}
for (i=0;i<=n*m;i++) {
for (auto tmp:e[i]) {
x=tmp.x,y=tmp.y,z=i;
xx=getfa(x),yy=getfa(y);
if (xx^yy) {
to[x].push_back(zyq(y,z));
to[y].push_back(zyq(x,z));
father[xx]=yy;
}
}
}
for (i=1;i<=p;i++) if (father[i]==i) dfs(i,0,0);
while (T--) {
read(x);read(y);
if (getfa(x)!=getfa(y)) puts("-1");
else printf("%d\n",query(x,y));
}
return 0;
}
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