#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w, n;
	cin >> h >> w >> n;
	vector<P>p(2 * n + 2);
	rep(i, n) {
		int a, b, c, d;
		cin >> a >> b >> c >> d;
		p[2 * i + 0] = { a,b };
		p[2 * i + 1] = { c,d };
	}
	p[2 * n + 0] = { 1,1 };
	p[2 * n + 1] = { h,w };
	vector <long long>dist(2 * n + 2, LINF);
	dist[2 * n + 0] = 0;
	vector<bool> done(2 * n + 2);
	rep(i, 2 * n + 2) {
		long long mn = LINF;
		int idx = -1;
		rep(j, 2 * n + 2) {
			if (done[j])continue;
			if (chmin(mn, dist[j])) {
				idx = j;
			}
		}
		done[idx] = true;
		rep(j, 2 * n + 2) {
			long long val = dist[idx] + abs(p[j].first - p[idx].first)
				+ abs(p[j].second - p[idx].second);
			chmin(dist[j], val);
		}
		if (idx < 2 * n && 0 == idx % 2) {
			chmin(dist[idx + 1], dist[idx] + 1);
		}
	}
	cout << dist.back() << endl;
	return 0;
}