#include <bits/stdc++.h>

using namespace std;
#define SZ(x) (int) (x).size()
#define REP(i, n) for(int i = 0; i < (n); i++)
#define FOR(i, a, b) for(auto i = (a); i < (b); i++)
#define For(i, a, b, c) \
	for(auto i = (a); i != (b); i += (c))
#define REPR(i, n) for(auto i = (n) -1; i >= 0; i--)
#define ALL(s) (s).begin(), (s).end()
#define so(V) sort(ALL(V))
#define rev(V) reverse(ALL(V))
#define uni(v) v.erase(unique(ALL(v)), (v).end())
#define eb emplace_back

typedef unsigned long long ull;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> PI;
typedef pair<ll, ll> PL;
const double EPS = 1e-6;
const int MOD = 1e9 + 7;
const int INF = (1 << 30);
const ll LINF = 1e18;
const double math_PI = acos(-1);

template<typename T>
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<class T>
bool chmax(T& a, const T& b) {
	if(a < b) {
		a = b;
		return true;
	}
	return false;
}

template<class T>
bool chmin(T& a, const T& b) {
	if(a > b) {
		a = b;
		return true;
	}
	return false;
}

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

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

template<typename T>
string join(vector<T>& vec, string splitter) {
	stringstream ss;
	REP(i, SZ(vec)) {
		if(i != 0) ss << splitter;
		ss << vec[i];
	}
	return ss.str();
}

template<typename T>
ostream& operator<<(ostream& os, vector<T>& vec) {
	os << join(vec, " ");
	return os;
}

#ifdef LOCAL
#include "./cpp-dump/dump.hpp"
#include "./cpp-dump/mytypes.hpp"
#define dump(...) cpp_dump(__VA_ARGS__)
namespace cp = cpp_dump;
#else
#define dump(...)
#define preprocess(...)
#define CPP_DUMP_SET_OPTION(...)
#define CPP_DUMP_DEFINE_EXPORT_OBJECT(...)
#define CPP_DUMP_DEFINE_EXPORT_ENUM(...)
#define CPP_DUMP_DEFINE_DANGEROUS_EXPORT_OBJECT(...)
#endif

void solve() {
	int H, W, N;
	cin >> H >> W >> N;
	vi a(N), b(N), c(N), d(N);
	REP(i, N) {
		cin >> a[i] >> b[i] >> c[i] >> d[i];
	}
	vb visited(N);
	priority_queue<PL, vector<PL>, greater<>> Q;
	REP(i, N) {
		Q.emplace(a[i] - 1 + b[i] - 1, i);
	}
	Q.emplace(H - 1 + W - 1, N);
	while(!Q.empty()) {
		auto [dist, ind] = Q.top();
		Q.pop();
		if(ind == N) {
			cout << dist << endl;
			return;
		}
		if(visited[ind]) continue;
		visited[ind] = true;
		dump(dist, ind);
		REP(i, N) {
			if(i == ind) continue;
			ll D = min(
				abs(a[i] - a[ind]) + abs(b[i] - b[ind]),
				abs(a[i] - c[ind]) + abs(b[i] - d[ind])
					+ 1);
			Q.emplace(D + dist, i);
		}
		ll D = min(H - a[ind] + W - b[ind],
				   H - c[ind] + W - d[ind] + 1)
			+ dist;
		Q.emplace(D, N);
		dump(D);
	}
}

int main() {
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	preprocess();
	solve();
	return 0;
}