#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int h, w, n;
  cin >> h >> w >> n;
  struct P {
    int x, y;
  };
  vector<P> p(2 * n + 2);
  rep(i, n) {
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    p[2 * i] = {a, b};
    p[2 * i + 1] = {c, d};
  }
  p[2 * n] = {1, 1};
  p[2 * n + 1] = {h, w};
  constexpr long long INF = 1002003004005006007;
  VL dist(2 * n + 2, INF);
  dist[2 * n] = 0;
  vector<char> done(2 * n + 2);
  rep(_, 2 * n + 2) {
    ll mn = INF;
    int imn = -1;
    rep(i, 2 * n + 2) if (!done[i] && chmin(mn, dist[i])) {
      imn = i;
    }
    done[imn] = true;
    rep(j, 2 * n + 2) {
      chmin(dist[j], dist[imn] + abs(p[j].x - p[imn].x) + abs(p[j].y - p[imn].y));
    }
    if (imn < 2 * n && imn % 2 == 0) {
      chmin(dist[imn + 1], dist[imn] + 1);
    }
  }
  cout << dist.back() << '\n';
}