#include <iostream>
#include <vector>
#include <algorithm>
#include <array>
#include <iterator>
#include <string>
#include <cctype>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cmath>
#include <ctime>
#include <iomanip>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <bitset>
#include <random>
#include <utility>
#include <functional>
using namespace std;
void Main()
{
	int H,W,N;
	cin >> H >> W >> N;
	vector<pair<int,int>> P(2 * N + 2);
	P[0] = make_pair(1,1);
	P[2 * N + 1] = make_pair(H,W);
	for(int i = 1;i <= N;i++)
	{
		int a,b,c,d;
		cin >> a >> b >> c >> d;
		P[2 * i - 1] = make_pair(a,b);
		P[2 * i] = make_pair(c,d);
	}
	vector<int> dp(2 * N + 2,(int)2e9);
	dp[0] = 0;
	priority_queue<pair<int,int>> Q;
	Q.push(make_pair(-0,0));
	while(!Q.empty())
	{
		int cur = -Q.top().first;
		int u = Q.top().second;
		Q.pop();
		if(dp[u] < cur)
		{
			continue;
		}
		if(u == 0)
		{
			for(int v = 1;v <= 2 * N + 1;v++)
			{
				int cost = abs(P[u].first - P[v].first) + abs(P[u].second - P[v].second);
				if(dp[v] > dp[u] + cost)
				{
					dp[v] = dp[u] + cost;
					Q.push(make_pair(-dp[v],v));
				}
			}
		}
		else if(u <= 2 * N)
		{
			for(int v = 1;v <= 2 * N + 1;v++)
			{
				int cost = abs(P[u].first - P[v].first) + abs(P[u].second - P[v].second);
				if((u & 1) && v == u + 1)
				{
					cost = 1;
				}
				if(dp[v] > dp[u] + cost)
				{
					dp[v] = dp[u] + cost;
					Q.push(make_pair(-dp[v],v));
				}
			}
		}
		else
		{
			break;
		}
	}
	cout << dp[2 * N + 1] << "\n";
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int tt = 1;
	/* cin >> tt; */
	while(tt--) Main();
}