## https://yukicoder.me/problems/no/2695

import heapq

MAX_INT = 10 ** 18

def main():
    H, W, N = map(int, input().split())
    warps = []
    for _ in range(N):
        a, b, c, d = map(int, input().split())
        warps.append((a, b, c, d))
    
    points = [(1, 1)]
    for a, b, c, d in warps:
        points.append((a, b)) 
    for a, b, c, d in warps:
        points.append((c, d))
    points.append((H, W)) 

    # dijkstra
    fix = [MAX_INT] * (2 * N + 2)
    seen = [MAX_INT] * (2 * N + 2)
    queue = []
    seen[0] = 0
    heapq.heappush(queue, (0, 0))
    while len(queue) > 0:
        cost, v = heapq.heappop(queue)
        if fix[v] < MAX_INT:
            continue

        fix[v] = cost
        # ワープ
        if 1 <= v <= N:
            w = v + N
            if fix[w] == MAX_INT:
                h_v, w_v = points[v]
                h_w, w_w = points[w]
                new_cost = cost + 1
                if seen[w] > new_cost:
                    seen[w] = new_cost
                    heapq.heappush(queue, (new_cost, w))

        # 普通の移動
        for w in range(2 * N + 2):
            if fix[w] < MAX_INT:
                continue

            h_v, w_v = points[v]
            h_w, w_w = points[w]
            new_cost = cost + (abs(h_v - h_w) + abs(w_v - w_w))
            if seen[w] > new_cost:
                seen[w] = new_cost
                heapq.heappush(queue, (new_cost, w))
                
    print(fix[-1])
  
    
























if __name__ == "__main__":
    main()