#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

template <typename CostType>
struct Edge {
  CostType cost;
  int src, dst;

  explicit Edge(const int src, const int dst, const CostType cost = 0)
      : cost(cost), src(src), dst(dst) {}

  auto operator<=>(const Edge& x) const = default;
};

template <typename CostType>
struct Dijkstra {
  const CostType inf;

  Dijkstra(const std::vector<std::vector<Edge<CostType>>>& graph,
           const CostType inf = std::numeric_limits<CostType>::max())
      : inf(inf), is_built(false), graph(graph) {}

  std::vector<CostType> build(const int s) {
    is_built = true;
    const int n = graph.size();
    std::vector<CostType> dist(n, inf);
    dist[s] = 0;
    prev.assign(n, -1);
    std::priority_queue<std::pair<CostType, int>,
                        std::vector<std::pair<CostType, int>>,
                        std::greater<std::pair<CostType, int>>> que;
    que.emplace(0, s);
    while (!que.empty()) {
      const auto [d, ver] = que.top();
      que.pop();
      if (d > dist[ver]) continue;
      for (const Edge<CostType>& e : graph[ver]) {
        if (dist[ver] + e.cost < dist[e.dst]) {
          dist[e.dst] = dist[ver] + e.cost;
          prev[e.dst] = ver;
          que.emplace(dist[e.dst], e.dst);
        }
      }
    }
    return dist;
  }

  std::vector<int> build_path(int t) const {
    assert(is_built);
    std::vector<int> res;
    for (; t != -1; t = prev[t]) {
      res.emplace_back(t);
    }
    std::reverse(res.begin(), res.end());
    return res;
  }

 private:
  bool is_built;
  std::vector<int> prev;
  std::vector<std::vector<Edge<CostType>>> graph;
};

int main() {
  int h, w, n; cin >> h >> w >> n;
  vector<vector<Edge<ll>>> graph(n * 2 + 2);
  vector<pair<int, int>> yx{{0, 0}, {h - 1, w - 1}};
  yx.reserve(n * 2 + 2);
  REP(i, n) {
    int a, b, c, d; cin >> a >> b >> c >> d; --a; --b; --c; --d;
    yx.emplace_back(a, b);
    yx.emplace_back(c, d);
    graph[i * 2 + 2].emplace_back(i * 2 + 2, i * 2 + 3, 1);
  }
  REP(i, n * 2 + 2) REP(j, n * 2 + 2) {
    if (i == j) continue;
    const auto [y1, x1] = yx[i];
    const auto [y2, x2] = yx[j];
    graph[i].emplace_back(i, j, abs(y1 - y2) + abs(x1 - x2));
  }
  cout << Dijkstra<ll>(graph).build(0)[1] << '\n';
  return 0;
}