#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int h, w, n;
    cin >> h >> w >> n;
    vector<int> a(2*n), b(2*n);
    rep(i,n) cin >> a[i] >> b[i] >> a[i+n] >> b[i+n];
    a.push_back(1);
    a.push_back(h);
    b.push_back(1);
    b.push_back(w);
    vector<ll> dist(2*n+2, 1e18);
    vector<int> used(2*n+2);
    dist[2*n] = 0;
    dbg(dist);
    rep(i,2*n+5){
        ll d = 1e18;
        int pos = -1;
        rep(j,2*n+2) {
            if(used[j]) continue;
            if(d>dist[j]) {
                d = dist[j];
                pos = j;
            }
        }
        dbg(d);
        dbg(pos);
        if(pos==-1) break;
        used[pos] = true;
        rep(j,2*n+2){
            dist[j] = min(dist[j], dist[pos] + abs(a[j]-a[pos])+abs(b[j]-b[pos]));
        }
        if(pos<n) {
            dist[pos+n] = min(dist[pos+n], dist[pos]+1);
        }
        dbg(dist);
    }
    cout << dist[2*n+1] << endl;
    return 0;
}