#include <bits/stdc++.h>
using namespace std;
#define all(v) (v).begin(), (v).end()
using ll = long long;
using ld = long double;
using pint = pair<int, int>;
using pll = pair<ll, ll>;

int main() {
    int H, W, N; cin >> H >> W >> N;
    vector<ll> a(N), b(N), c(N), d(N);
    for (int i = 0; i < N; i++) {
        cin >> a[i] >> b[i] >> c[i] >> d[i];
        a[i]--, b[i]--, c[i]--, d[i]--;
    }
    priority_queue<pll, vector<pll>, greater<pll>> que;
    que.push({0, 0});
    ll ans = 2e9 + 7;
    vector<ll> md(N, 2e9+7);
    while(!que.empty()) {
        auto [dist, pos] = que.top(); que.pop();
        ll y = pos/W, x = pos%W;
        if (dist >= ans) break;
        ans = min(ans, dist+(H-1-y)+(W-1-x));
        for (int i = 0; i < N; i++) {
            ll ndist = dist+abs(a[i]-y)+abs(b[i]-x)+1;
            if (ndist >= md[i] || ndist >= ans) continue;
            md[i] = ndist;
            que.push({ndist, c[i]*W+d[i]});
        }
    }
    cout << ans << endl;
}