#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int inf = (int)2e9 + 1;

int H, W, N;
int X[2020], Y[2020];
int dist[2020], used[2020];
int main(void){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    
    cin >> H >> W >> N;
    int cnt = 1;
    X[0] = 1, Y[0] = 1;
    for(int i = 0;i < N;i++){
        int a, b, c, d; cin >> a >> b >> c >> d;
        X[cnt] = a, Y[cnt] = b;
        cnt++;
        X[cnt] = c, Y[cnt] = d;
        cnt++;
    }
    X[cnt] = H, Y[cnt] = W; cnt++;
    for(int i = 1;i < cnt;i++)dist[i] = inf;
    while(1){
        int v = -1, d = inf;
        for(int i = 0;i < cnt;i++)if(!used[i]){
            if(d > dist[i])v = i, d = dist[i];
        }
        used[v] = 1;
        if(v == -1)break;
        for(int nv = 0;nv < cnt;nv++){
            ll tmp = d + abs(X[v] - X[nv]) + abs(Y[v] - Y[nv]);
            if(v % 2 == 1 && nv == v + 1)tmp = d + 1;
            if(tmp > inf)continue;
            int nd = tmp;
            dist[nv] = min(dist[nv], nd);
        }
    }
    cout << dist[cnt - 1] << endl;
    return 0;
}