#include <bits/stdc++.h>
#ifdef LOCAL
#include "./debug.cpp"
#else
#define debug(...)
#define print_line
#endif
using namespace std;
using ll = long long;

template <typename T>
vector<T> dijkstra(const vector<vector<pair<int, T>>> &G, int start = 0) {
    int n = G.size();
    vector<T> dst(n, numeric_limits<T>::max());
    priority_queue<pair<T, int>> pq;
    dst[start] = 0;
    pq.push(make_pair(0, start));
    while (!pq.empty()) {
        auto [dst_sum, now] = pq.top();
        pq.pop();
        dst_sum = -dst_sum;
        if (dst[now] < dst_sum) continue;
        for (auto [nxt, cost] : G[now]) {
            if (dst[nxt] > dst[now] + cost) {
                dst[nxt] = dst[now] + cost;
                pq.push(make_pair(-dst[nxt], nxt));
            }
        }
    }
    return dst;
}

int main() {
    int H, W, N;
    cin >> H >> W >> N;

    vector<array<int, 4>> E(N);
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < 4; j++) {
            cin >> E[i][j];
            E[i][j]--;
        }
    }

    vector<vector<pair<int, ll>>> G(2 * N + 2);
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < 4; j++) {
            G[2 * N].push_back({2 * i, E[i][0] + E[i][1]});
            G[2 * i].push_back({2 * N, E[i][0] + E[i][1]});
            G[2 * N + 1].push_back({2 * i, H - E[i][0] + W - E[i][1] - 2});
            G[2 * i].push_back({2 * N + 1, H - E[i][0] + W - E[i][1] - 2});
            G[2 * N].push_back({2 * i + 1, E[i][2] + E[i][3]});
            G[2 * i + 1].push_back({2 * N, E[i][2] + E[i][3]});
            G[2 * N + 1].push_back({2 * i + 1, H - E[i][2] + W - E[i][3] - 2});
            G[2 * i + 1].push_back({2 * N + 1, H - E[i][2] + W - E[i][3] - 2});
            G[2 * i].push_back({2 * i + 1, 1});
        }
    }
    G[2 * N].push_back({2 * N + 1, H + W - 2});
    G[2 * N + 1].push_back({2 * N, H + W - 2});

    vector<ll> dst = dijkstra(G, 2 * N);

    cout << dst[2 * N + 1] << endl;
}