#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

const ll INF = 10000000000000023LL;

int main() {
    ll H, W, N;
    cin >> H >> W >> N;
    vector<ll> a(N);
    vector<ll> b(N);
    vector<ll> c(N);
    vector<ll> d(N);
    rep(i, N){
        cin >> a[i] >> b[i] >> c[i] >> d[i];
        a[i]--;
        b[i]--;
        c[i]--;
        d[i]--;
    }
    map<pll, ll> mp;
    mp[make_pair(0, 0)]++;
    mp[make_pair(H - 1, W - 1)]++;
    rep(i, N){
        mp[make_pair(a[i], b[i])]++;
        mp[make_pair(c[i], d[i])]++;
    }

    ll now = 0;
    vector<pll> p;
    for (auto it = mp.begin(); it != mp.end(); it++){
        p.push_back(it->first);
        it->second = now;
        now++;
    }
    vector<vector<ll>> vec(now, vector<ll>(now));
    rep(i, now){
        rep(j, now){
            vec[i][j] = abs(p[i].first - p[j].first) + abs(p[i].second - p[j].second);
        }
    }
    rep(i, N){
        vec[mp[make_pair(a[i], b[i])]][mp[make_pair(c[i], d[i])]] = 1;
    }
    // debug(vec);
    vector<ll> visited(now, false);
    vector<ll> dist(now, INF);
    dist[mp[make_pair(0, 0)]] = 0;
    for (ll i = 0; i < now; i++){
        ll min_d = INF;
        ll min_id = -1;
        rep(j, now){
            if (!visited[j] && min_d > dist[j]){
                min_d = dist[j];
                min_id = j;
            }
        }
        visited[min_id] = true;
        for (ll j = 0; j < now; j++){
            if (min_d + vec[min_id][j] < dist[j]){
                dist[j] = min_d + vec[min_id][j];
            }
        }
    }
    debug(dist);
    cout << dist[mp[make_pair(H - 1, W - 1)]] << endl;
}