#include<bits/stdc++.h>
#include<atcoder/all>

using namespace std;

using int64 = long long;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;

template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 >& p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  explicit FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint<F>{forward<F>(f)};
}


int main() {
  int H, W, N;
  cin >> H >> W >> N;
  vector< int > A(N), B(N), C(N), D(N);
  vector< int > ys, xs;
  for(int i = 0; i < N; i++) {
    cin >> A[i] >> B[i] >> C[i] >> D[i];
    --A[i], --B[i], --C[i], --D[i];
    ys.emplace_back(A[i]);
    xs.emplace_back(B[i]);
    ys.emplace_back(C[i]);
    xs.emplace_back(D[i]);
  }
  ys.emplace_back(0);
  ys.emplace_back(H - 1);
  xs.emplace_back(0);
  xs.emplace_back(W - 1);
  sort(ys.begin(), ys.end());
  sort(xs.begin(), xs.end());
  ys.erase(unique(ys.begin(), ys.end()), ys.end());
  xs.erase(unique(xs.begin(), xs.end()), xs.end());
  auto mp = make_v< int >(ys.size(), xs.size());
  fill_v(mp, -1);
  for(int i = 0; i < N; i++) {
    A[i] = lower_bound(ys.begin(), ys.end(), A[i]) - ys.begin();
    B[i] = lower_bound(xs.begin(), xs.end(), B[i]) - xs.begin();
    C[i] = lower_bound(ys.begin(), ys.end(), C[i]) - ys.begin();
    D[i] = lower_bound(xs.begin(), xs.end(), D[i]) - xs.begin();
    mp[A[i]][B[i]] = i;
  }
  auto dp = make_v< int64 >(ys.size(), xs.size());
  fill_v(dp, infll);
  dp[0][0] = 0;
  using ti = tuple< int64, int, int >;
  priority_queue< ti, vector< ti >, greater<>> que;
  que.emplace(0, 0, 0);
  const int vy[] = {0, -1, 0, 1};
  const int vx[] = {-1, 0, 1, 0};
  while(not que.empty()) {
    auto [cost, y, x] = que.top();
    que.pop();
    if(dp[y][x] < cost) continue;
    if(~mp[y][x]) {
      int ny = C[mp[y][x]], nx = D[mp[y][x]];
      if (chmin(dp[ny][nx], cost + 1)) {
        que.emplace(dp[ny][nx], ny, nx);
      }
    }
    for(int i = 0; i < 4; i++) {
      int ny = y + vy[i];
      int nx = x + vx[i];
      if(ny < 0 or nx < 0 or ny >= ys.size() or nx >= xs.size()) {
        continue;
      }
      if(chmin(dp[ny][nx], cost + abs(ys[ny] - ys[y]) + abs(xs[nx] - xs[x]))) {
        que.emplace(dp[ny][nx], ny, nx);
      }
    }
  }
  cout << dp.back().back() << endl;
}