#include<bits/stdc++.h>
using namespace std;
#define int long long
using Graph=vector<vector<pair<int,int>>>;

vector<int> dijkstra(vector<vector<pair<int,int>>> G,int v){
	int N=(int)(G.size());
	vector<int> cur(N,2000000000000LL);
	vector<bool> kakutei(N,false);
    priority_queue<pair<int,int>,vector<pair<int,int>>,greater<pair<int,int>>> que;
    cur[v]=0;
    que.push(make_pair(cur[v],v));
    while(!que.empty()){
        int pos=que.top().second;
        que.pop();
        if(kakutei[pos]==true){
            continue;
        }
        kakutei[pos]=true;
        for(pair<int,int> i : G[pos]){
            int nex=i.first;
            int cost=i.second;
            if(cur[nex]>cur[pos]+cost){
                cur[nex]=cur[pos]+cost;
                que.push(make_pair(cur[nex],nex));
            }
        }
    }
	return cur;
}

signed main(){
	int H,W,N;
	cin >> H >> W >> N;
	//辺数O(N^2)本，頂点数O(N)の重み付き最短経路
	//dijkstraでO(N^2 log N)
	Graph G(2*N+2);
	vector<pair<int,int>> start(N);
	vector<pair<int,int>> goal(N);
	for(int i=0;i<N;i++){
		cin >> start[i].first >> start[i].second >> goal[i].first >> goal[i].second;
	}
	G[0].push_back(make_pair(2*N+1,H-1+W-1));
	G[2*N+1].push_back(make_pair(0,H-1+W-1));
	for(int i=0;i<N;i++){
		G[2*i+1].push_back(make_pair(2*i+2,1));
		G[0].push_back(make_pair(2*i+1,start[i].first+start[i].second-2));
		G[0].push_back(make_pair(2*i+2,goal[i].first+goal[i].second-2));
		G[2*i+1].push_back(make_pair(0,start[i].first+start[i].second-2));
		G[2*i+2].push_back(make_pair(0,goal[i].first+goal[i].second-2));
		G[2*i+1].push_back(make_pair(2*N+1,H-start[i].first+W-start[i].second));
		G[2*N+1].push_back(make_pair(2*i+1,H-start[i].first+W-start[i].second));
		G[2*i+2].push_back(make_pair(2*N+1,H-goal[i].first+W-goal[i].second));
		G[2*N+1].push_back(make_pair(2*i+2,H-goal[i].first+W-goal[i].second));
	}
	for(int i=0;i<N;i++){
		for(int j=0;j<N;j++){
			if(i==j){
				continue;
			}
			G[2*i+1].push_back(make_pair(2*j+1,abs(start[j].first-start[i].first)+abs(start[j].second-start[i].second)));
			G[2*i+1].push_back(make_pair(2*j+2,abs(goal[j].first-start[i].first)+abs(goal[j].second-start[i].second)));
			G[2*i+2].push_back(make_pair(2*j+1,abs(start[j].first-goal[i].first)+abs(start[j].second-goal[i].second)));
			G[2*i+2].push_back(make_pair(2*j+2,abs(goal[j].first-goal[i].first)+abs(goal[j].second-goal[i].second)));
		}
	}
	vector<int> cur=dijkstra(G,0);
	cout << cur[2*N+1] << endl;
}