#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(),(v).end()
#define pb(a) push_back(a)
#define rep(i, n) for(int i=0;i<n;i++)
#define foa(e, v) for(auto&& e : v)
using ll = long long;
const ll MOD7 = 1000000007, MOD998 = 998244353, INF = (1LL << 60);
#define dout(a) cout<<fixed<<setprecision(10)<<a<<endl;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll h, w, n;
    cin >> h >> w >> n;
    vector<pair<ll, ll>> v(n * 2 + 2);
    vector<ll> dis(n * 2 + 2, INF);
    dis[n * 2] = 0;
    v[n * 2] = {1, 1};
    v[n * 2 + 1] = {h, w};
    rep(i, n) {
        ll a, b, c, d;
        cin >> a >> b >> c >> d;
        v[i * 2] = {a, b};
        v[i * 2 + 1] = {c, d};
    }
    // now % 2 == 0 and now < n * 2 -> now + 1 : dis + 1
    using P = pair<ll, ll>;
    priority_queue<P, vector<P>, greater<P> > Q;
    Q.push({0, n * 2});
    while(!Q.empty()){
        P p = Q.top();
        Q.pop();
        ll cur = p.second;
        if(dis[cur] < p.first) continue;
        rep(i, n * 2 + 2) {
            if(dis[i] > abs(v[cur].first - v[i].first) + abs(v[cur].second - v[i].second) + dis[cur]) {
                dis[i] = abs(v[cur].first - v[i].first) + abs(v[cur].second - v[i].second) + dis[cur];
                Q.push({dis[i], i});
            }
        }
        if(cur % 2 == 0 and cur < n * 2) {
            if(dis[cur + 1] > dis[cur] + 1) {
                dis[cur + 1] = dis[cur] + 1;
                Q.push({dis[cur + 1], cur + 1});
            }
        }
    }
    cout << dis.back() << endl;
    return 0;
}