#include <bits/stdc++.h>
using namespace std;

using pii = pair<int, int>;

template<class T> bool chmin(T &a, const T &x) { return x < a ? a = x, true : false; }

int md(pii const &p1, pii const &p2) {
  return abs(p1.first - p2.first) + abs(p1.second - p2.second);
}

int main() {
  int H, W, N;
  cin >> H >> W >> N;
  vector<pii> P(N+N);
  for (int i = 0; i < N; ++i)
    cin >> P[i].first >> P[i].second >> P[N+i].first >> P[N+i].second;

  int const S=N+N, T=N+N+1;
  vector<vector<pii>> G(N+N+2);  // cost, to_id
  G[S].emplace_back(md({1, 1}, {H, W}), T);
  for (int i = 0; i < N+N; ++i) {
    G[S].emplace_back(md({1, 1}, P[i]), i);
    G[i].emplace_back(md(P[i], {H, W}), T);
  }
  for (int i = 0; i < N+N; ++i)
  for (int j = 0; j < N+N; ++j)
  if (i != j) {
    if (N+i == j)
      G[i].emplace_back(1, j);
    else
      G[i].emplace_back(md(P[i], P[j]), j);
  }

  vector<int> answer(N+N+2, 2e9+9);
  priority_queue<pii, vector<pii>, greater<void>> pq;  // distance, id
  answer[S] = 0;
  pq.emplace(0, S);
  while (!pq.empty()) {
    auto const [d, u] = pq.top();
    pq.pop();
    if (d > answer[u])
      continue;
    for (auto const &[c, v] : G[u])
      if (chmin(answer[v], d + c))
        pq.emplace(d+c, v);
  }

  cout << answer[T] << endl;
}