#include <bits/stdc++.h>
using namespace std;
const long long INF = 1000000000000;
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];
    a[i]--;
    b[i]--;
    c[i]--;
    d[i]--;
  }
  vector<long long> x(N * 2 + 2), y(N * 2 + 2);
  for (int i = 0; i < N; i++){
    x[i * 2] = a[i];
    y[i * 2] = b[i];
    x[i * 2 + 1] = c[i];
    y[i * 2 + 1] = d[i];
  }
  x[N * 2] = 0;
  y[N * 2] = 0;
  x[N * 2 + 1] = H - 1;
  y[N * 2 + 1] = W - 1;
  vector<bool> used(N * 2 + 2, false);
  vector<long long> D(N * 2 + 2, INF);
  D[N * 2] = 0;
  for (int i = 0; i < N * 2 + 2; i++){
    int p = -1;
    for (int j = 0; j < N * 2 + 2; j++){
      if (!used[j]){
        if (p == -1){
          p = j;
        } else if (D[j] < D[p]){
          p = j;
        }
      }
    }
    used[p] = true;
    for (int k = 0; k < N * 2 + 2; k++){
      D[k] = min(D[k], D[p] + abs(x[k] - x[p]) + abs(y[k] - y[p]));
    }
    if (p < N * 2 && p % 2 == 0){
      D[p + 1] = min(D[p + 1], D[p] + 1);
    }
  }
  cout << D[N * 2 + 1] << endl;
}