MUD

#include <bits/stdc++.h>
#define FOR(i,a,b) for(i=a;i<=b;i++)
using namespace std;
#define mp(x,y) make_pair(x,y)
int h,k,i,N,a[5010],b[5010],t,u,d[1005][1005],j,x,y;
std::queue < pair<int,int> > q;
bool kt[2005][2005];
int main(){
    cin>>h>>k>>N;
    FOR(i,0,1005)
    FOR(j,0,1005) { kt[i][j]=true; d[i][j]=INT_MAX-1;}
    FOR(i,1,N){ cin>>a[i]>>b[i]; kt[a[i]+501][b[i]+501]=false;}
    d[h+501][k+501]=0;
    q.push(mp(h,k));
    //cout<<endl;
    while (q.size()!=0)
    {
       x=q.front().first;
       y=q.front().second;
       kt[x+501][y+501]=false;
       if ((abs(x)<=500) && (abs(y)<=500))
       {
       if (kt[x+501+1][y+501]==true) { q.push(mp(x+1,y)); kt[x+501+1][y+501]=false;}
       if (kt[x+501-1][y+501]==true) { q.push(mp(x-1,y)); kt[x+501-1][y+501]=false;}
       if (kt[x+501][y+501+1]==true) { q.push(mp(x,y+1)); kt[x+501][y+501+1]=false;}
       if (kt[x+501][y+501-1]==true) { q.push(mp(x,y-1)); kt[x+501][y+501-1]=false;}
       }
       d[x+501][y+501]=min(min(min(min(d[x+1+501][y+501]+1,d[x-1+501][y+501]+1),d[x+501][y+501-1]+1),d[x+501][y+501+1]+1),d[x+501][y+501]);
       if ((x==0)&& (y==0)) break;
       q.pop();
      // cout<<x<<" "<<y<<" "<<d[x+501][y+501]<<endl;
    }
    cout<<d[501][501];
    return 0;
}