#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
int a,b,n,m;
int f[510][510];
int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
struct node{
	int x,y,time; 
	bool used=0;
}now,net;
struct id{
	int x,y;
}f1[510*510];
queue<node> q;
bool in(int x,int y){
	return x>=0&&x<n&&y>=0&&y<m;
}
int cnt=0;
int bfs(){
	now.x=f1[++cnt].x,now.y=f1[++cnt].y;
	q.push(now);
	f[now.x][now.y]=0;
	while(!q.empty()){
		now=q.front();
		q.pop();
		if(f[now.x][now.y]==2){
			return now.time;
		}
		for(int i=0;i<4;i++){
			net.x=now.x+dx[i];
			net.y=now.y+dy[i];
			net.time=now.time++;
			if(in(net.x,net.y)&&!net.used){
				q.push(net);
				net.used=114514;
			}
		}
	}
}
int main(){
	cin>>n>>m>>a>>b;
	for(int i=0;i<a;i++){
		int x1,y1;
		cin>>x1>>y1;
		f[x1][y1]=1;
		f1[i].x=x1;
		f1[i].y=y1;
	}
	for(int i=0;i<b;i++){
		int x1,y1;
		cin>>x1>>y1;
		f[x1][y1]=2;
		f1[a+i-1].x=x1;
		f1[a+i-1].y=y1;
	}
	cout<<bfs();
	return 0;
}