from heapq import heappush, heappop

def dijkstra(s, N): # (始点, ノード数)
    dist = [INF for _ in range(N)]
    hq = [(0, s)]
    dist[s] = 0
    seen = [False] * N # ノードが確定済みかどうか
    while hq:
        d, v = heappop(hq) # ノードを pop する
        if seen[v]:
            continue
        seen[v] = True
        for to, cost in G[v]: # ノード v に隣接しているノードに対して
            if dist[v] + cost < dist[to]:
                dist[to] = dist[v] + cost
                heappush(hq, (dist[to], to))
    return dist

import sys
input = sys.stdin.readline
H, W, N = map(int, input().split())
ABCD = [list(map(int, input().split())) for _ in range(N)]
G = [[] for _ in range(2*N+2)]
INF = H+W
st = 2*N
ed = 2*N+1
G[st].append((ed, H-1+W-1))
G[ed].append((st, H-1+W-1))
for i in range(N):
    a, b, c, d = ABCD[i]
    u = i*2
    v = i*2+1
    G[u].append((v, 1))
    G[v].append((u, abs(c-a)+abs(d-b)))
    G[st].append((u, a-1+b-1))
    G[u].append((st, a-1+b-1))
    G[ed].append((u, H-a+W-b))
    G[u].append((ed, H-a+W-b))
    G[st].append((v, c-1+d-1))
    G[v].append((st, c-1+d-1))
    G[ed].append((v, H-c+W-d))
    G[v].append((ed, H-c+W-d))
for i in range(N):
    a, b, c, d = ABCD[i]
    u = i*2
    v = i*2+1
    for j in range(i+1, N):
        a2, b2, c2, d2 = ABCD[j]
        u2 = j*2
        v2 = j*2+1
        G[u].append((u2, abs(a2-a)+abs(b2-b)))
        G[u2].append((u, abs(a2-a)+abs(b2-b)))
        G[u].append((v2, abs(c2-a)+abs(d2-b)))
        G[v2].append((u, abs(c2-a)+abs(d2-b)))
        G[v].append((u2, abs(a2-c)+abs(b2-d)))
        G[u2].append((v, abs(a2-c)+abs(b2-d)))
        G[v].append((v2, abs(c2-c)+abs(d2-d)))
        G[v2].append((v, abs(c2-c)+abs(d2-d)))

dist = dijkstra(st, 2*N+2)
print(dist[ed])