#pragma GCC optimize("O2")
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfenv>
#include <cfloat>
#include <chrono>
#include <cinttypes>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdarg>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <streambuf>
#include <string>
#include <tuple>
#include <type_traits>
#include <variant>

#if __cplusplus >= 202002L

#include <bit>
#include <compare>
#include <concepts>
#include <numbers>
#include <ranges>
#include <span>

#else

#define ssize(v) (int)(v).size()
#define popcount(x) __builtin_popcountll(x)
constexpr int bit_width(const unsigned int x) { return x == 0 ? 0 : ((sizeof(unsigned int) * CHAR_BIT) - __builtin_clz(x)); }
constexpr int bit_width(const unsigned long long x) { return x == 0 ? 0 : ((sizeof(unsigned long long) * CHAR_BIT) - __builtin_clzll(x)); }
constexpr int countr_zero(const unsigned int x) { return x == 0 ? sizeof(unsigned int) * CHAR_BIT : __builtin_ctz(x); }
constexpr int countr_zero(const unsigned long long x) { return x == 0 ? sizeof(unsigned long long) * CHAR_BIT : __builtin_ctzll(x); }
constexpr unsigned int bit_ceil(const unsigned int x) { return x == 0 ? 1 : (popcount(x) == 1 ? x : (1u << bit_width(x))); }
constexpr unsigned long long bit_ceil(const unsigned long long x) { return x == 0 ? 1 : (popcount(x) == 1 ? x : (1ull << bit_width(x))); }

#endif

//#define int ll
#define INT128_MAX (__int128)(((unsigned __int128) 1 << ((sizeof(__int128) * __CHAR_BIT__) - 1)) - 1)
#define INT128_MIN (-INT128_MAX - 1)

#define clock chrono::steady_clock::now().time_since_epoch().count()

#ifdef DEBUG
#define dbg(x) cout << (#x) << " = " << x << '\n'
#else
#define dbg(x)
#endif

using namespace std;

using ll = long long;
using ull = unsigned long long;
using ldb = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
//#define double ldb

template<class T>
ostream& operator<<(ostream& os, const pair<T, T> pr) {
  return os << pr.first << ' ' << pr.second;
}
template<class T, size_t N>
ostream& operator<<(ostream& os, const array<T, N> &arr) {
  for(const T &X : arr)
    os << X << ' ';
  return os;
}
template<class T>
ostream& operator<<(ostream& os, const vector<T> &vec) {
  for(const T &X : vec)
    os << X << ' ';
  return os;
}
template<class T>
ostream& operator<<(ostream& os, const set<T> &s) {
  for(const T &x : s)
    os << x << ' ';
  return os;
}

template<class T>
pair<vector<T>, vector<int>> Dijkstra(vector<vector<pair<int, T>>> &g, int s) {
  int n = ssize(g);
  vector<T> dis(n, -1);
  vector<int> pre(n, -1);
  priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> pq;

  dis[s] = 0;
  pq.push({0, s});

  while(!pq.empty()) {
    auto [d, v] = pq.top(); pq.pop();
    if (dis[v] != d) continue;
    for(auto [x, w] : g[v]) {
      if (dis[x] != -1 and d + w >= dis[x]) continue;
      dis[x] = d + w, pre[x] = v;
      pq.push(make_pair(d + w, x));
    }
  }

  return make_pair(dis, pre);
}

signed main() {
  ios::sync_with_stdio(false), cin.tie(NULL);

  int h, w, n; cin >> h >> w >> n;
  vector<array<int, 4>> warp(n);
  for(auto &[a, b, c, d] : warp)
    cin >> a >> b >> c >> d;
  warp.push_back({h, w, 1, 1});

  vector<vector<pair<int, ll>>> g(2 * n + 2);
  for(int i = 0; i <= n; i++)
    g[i].emplace_back(i + (n + 1), 1);
  for(int i = n + 1; i < 2 * (n + 1); i++)
    for(int j = 0; j <= n; j++)
      g[i].emplace_back(j, abs(warp[i - n - 1][2] - warp[j][0]) + abs(warp[i - n - 1][3] - warp[j][1]));

  cout << Dijkstra(g, 2 * n + 1).first[n] << '\n';

  return 0;
}