#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, n) for(int i = a; i < n; i++)
#define rrep(i, a, n) for(int i = a; i >= n; i--)
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
// constexpr ll MOD = 1000000007;
constexpr ll MOD = 998244353;
constexpr int IINF = 1001001001;
constexpr ll INF = 1LL<<60;

template<class t,class u> void chmax(t&a,u b){if(a<b)a=b;}
template<class t,class u> void chmin(t&a,u b){if(b<a)a=b;}

vector<ll> dijk(ll s, vector<vector<pll>> &g){
    priority_queue<pll, vector<pll>, greater<pll>> que;
    vector<ll> dist(g.size(), (1LL<<60));
    que.push(make_pair(0, s));
    dist[s] = 0;
    while(!que.empty()){
        pll q = que.top(); que.pop();
        ll d = q.first, u = q.second;
        if(dist[u] < d) continue;
        for(auto nq: g[u]){
            ll v = nq.first, cost = nq.second;
            if(dist[v] > d+cost){
                dist[v] = d+cost;
                que.push({dist[v], v});
            }
        }
    }
    return dist;
}

int main(){
    int h, w, n; cin >> h >> w >> n;
    vector<vector<pair<ll, ll>>> g(2*n+2);
    vector<ll> a(n), b(n), c(n), d(n);
    rep(i, 0, n) cin >> a[i] >> b[i] >> c[i] >> d[i];
    rep(i, 0, n){
        g[2*i].push_back({2*i+1, 1});        
        g[2*i+1].push_back({2*i, abs(a[i]-c[i])+abs(b[i]-d[i])});        
    }
    rep(i, 0, n){
        rep(j, i+1, n){
            g[2*i].push_back({2*j, abs(a[i]-a[j])+abs(b[i]-b[j])});        
            g[2*j].push_back({2*i, abs(a[i]-a[j])+abs(b[i]-b[j])});        
            g[2*i].push_back({2*j+1, abs(a[i]-c[j])+abs(b[i]-d[j])}); 
            g[2*j+1].push_back({2*i, abs(a[i]-c[j])+abs(b[i]-d[j])}); 
            g[2*i+1].push_back({2*j, abs(c[i]-a[j])+abs(d[i]-b[j])});        
            g[2*j].push_back({2*i+1, abs(c[i]-a[j])+abs(d[i]-b[j])});        
            g[2*i+1].push_back({2*j+1, abs(c[i]-c[j])+abs(d[i]-d[j])}); 
            g[2*j+1].push_back({2*i+1, abs(c[i]-c[j])+abs(d[i]-d[j])}); 
        }
    }
    rep(i, 0, n){
        g[2*n].push_back({2*i, a[i]-1+b[i]-1});
        g[2*i].push_back({2*n+1, h-a[i]+w-b[i]});
        g[2*i+1].push_back({2*n+1, h-c[i]+w-d[i]});
    }
    g[2*n].push_back({2*n+1, h+w});
    vector<ll> dist = dijk(2*n, g);
    cout << dist[2*n+1] << endl;

    return 0;
}