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

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];

  using V = pair<int, int>;  // i, j
  using E = tuple<int, int, int>;  // cost, i, j
  map<V, vector<E>> G;
  for (int i = 0; i < N; ++i) {
    G[{1, 1}].emplace_back(A[i]-1 + B[i]-1, A[i], B[i]);
    G[{1, 1}].emplace_back(C[i]-1 + D[i]-1, C[i], D[i]);
    for (int j = 0; j < N; ++j)
      if (i != j) {
        G[{A[i], B[i]}].emplace_back(abs(A[j]-A[i])+abs(B[j]-B[i]), A[j], B[j]);
        G[{A[i], B[i]}].emplace_back(abs(C[j]-A[i])+abs(D[j]-B[i]), C[j], D[j]);
        G[{C[i], D[i]}].emplace_back(abs(A[j]-C[i])+abs(B[j]-D[i]), A[j], B[j]);
        G[{C[i], D[i]}].emplace_back(abs(C[j]-C[i])+abs(D[j]-D[i]), C[j], D[j]);
      }
    G[{A[i], B[i]}].emplace_back(1, C[i], D[i]);
    G[{A[i], B[i]}].emplace_back(H-A[i] + W-B[i], H, W);
    G[{C[i], D[i]}].emplace_back(H-C[i] + W-D[i], H, W);
  }
  G[{1, 1}].emplace_back(H-1 + W-1, H, W);

  map<V, int> answer;
  priority_queue<E, vector<E>, greater<void>> pq;  // distance, i, j
  pq.emplace(0, 1, 1);
  while (!pq.empty()) {
    auto const [d, i, j] = pq.top();
    pq.pop();
    answer.try_emplace(V(i, j), d);
    if (d > answer[{i, j}])
      continue;
    for (auto const &[c, i2, j2] : G[{i, j}]) {
      answer.try_emplace(V(i2, j2), d+c);
      if (d+c <= answer[{i2, j2}]) {
        answer[{i2, j2}] = d+c;
        pq.emplace(d+c, i2, j2);
      }
    }
  }

  cout << answer[{H, W}] << endl;
}