#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<int> a(N), b(N), c(N), d(N);
    for (int i = 0; i < N; i++) {
        cin >> a[i] >> b[i] >> c[i] >> d[i];
    }
    priority_queue<pair<int, pint>, vector<pair<int, pint>>, greater<pair<int, pint>>> que;
    que.push({0, {1, 1}});
    int ans = 2e9 + 7;
    while(!que.empty()) {
        auto [dist, p] = que.top(); que.pop();
        auto [y, x] = p;
        if (dist >= ans) break;
        ans = min(ans, dist+(H-y)+(W-x));
        for (int i = 0; i < N; i++) {
            auto np = make_pair(c[i], d[i]);
            que.push({dist+abs(a[i]-y)+abs(b[i]-x)+1, np});
        }
    }
    cout << ans << endl;
}