#include <bits/stdc++.h>

using namespace std;
void fast_io() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
}

int main() {
    fast_io();
    int n;
    long long h, w;
    cin >> h >> w >> n;

    vector<pair<long long, long long>> points{{1, 1}, {h, w}};
    vector<vector<long long>> dist(2 * n + 2, vector<long long>(2 * n + 2, 0));
    for (int i = 0; i < n; i++) {
        long long a, b, c, d;
        cin >> a >> b >> c >> d;
        points.push_back({a, b});
        points.push_back({c, d});
        dist[2 * i + 2][2 * i + 3] = 1;
    }
    for (int i = 0; i < 2 * n + 2; i++) {
        for (int j = 0; j < 2 * n + 2; j++) {
            if (dist[i][j]) {
                continue;
            }
            dist[i][j] = abs(points[i].first - points[j].first) +
                         abs(points[i].second - points[j].second);
        }
    }
    const long long INF = 1e18;
    vector<bool> vis(2 * n + 2, false);
    vector<long long> ans(2 * n + 2, INF);
    ans[0] = 0;
    for (int i = 0; i < 2 * n + 2; i++) {
        int v = -1;
        long long ma = INF;
        for (int j = 0; j < 2 * n + 2; j++) {
            if (!vis[j] && ans[j] < ma) {
                ma = ans[j];
                v = j;
            }
        }
        if (v == -1) {
            break;
        }
        vis[v] = true;
        for (int u = 0; u < 2 * n + 2; u++) {
            ans[u] = min(ans[u], ans[v] + dist[v][u]);
        }
    }
    cout << ans[1] << endl;
}