#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define ALL(v) v.begin(), v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

const ll INF=1LL<<60;

struct Edge{
  int to;
  ll w;
  Edge(int to,ll w) : to(to),w(w) {}
};

using Graph=vector<vector<Edge>>;
using pli=pair<ll,int>;

template<class T> bool chmin(T& a,T b){
  if(a>b){
    a=b;
    return true;
  }
  return false;
}

int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);

  ll h,w,n;
  cin>>h>>w>>n;
  vector<ll> A(n),B(n),C(n),D(n);
  rep(i,n){
    cin>>A[i]>>B[i]>>C[i]>>D[i];
    A[i]--,B[i]--,C[i]--,D[i]--;
  }
  
  Graph G(2*n+2);
  rep(i,n){
    G[i].push_back(Edge(i+n,1));
  }
  G[2*n].push_back(Edge(2*n+1,h+w-2));
  rep(i,n){
     G[2*n].push_back(Edge(i,A[i]+B[i]));
     G[i+n].push_back(Edge(2*n+1,h+w-2-C[i]-D[i]));
  }
  rep(i,n){
    rep(j,n){
      G[i].push_back(Edge(j,abs(A[i]-A[j])+abs(B[i]-B[j])));
      G[i+n].push_back(Edge(j,abs(C[i]-A[j])+abs(D[i]-B[j])));
    }
  }
  
  vector<ll> dist(2*n+2,INF);
  int s=2*n;
  dist[s]=0;
  
  priority_queue<pli,vector<pli>,greater<pli>> que;
  que.push({dist[s],s});
  
  while(!que.empty()){
    int v=que.top().second;
    ll d=que.top().first;
    que.pop();
    
    if(d>dist[v]) continue;
    
    for(auto e:G[v]){
      if(chmin(dist[e.to],dist[v]+e.w)){
        que.push({dist[e.to],e.to});
      }
    }
  }
  cout<<dist[2*n+1]<<endl;
  
  return 0;
}