from collections import defaultdict

INF = float("INF")
H, W, N = map(int, input().split())


def encode(i, j):
   return i*W + j


G = defaultdict(list)

Ps = [(0, 0), (H-1, W-1)]
for _ in range(N):
   a, b, c, d = map(lambda x: int(x) - 1, input().split())
   P = encode(a, b)
   Q = encode(c, d)
   G[P].append((Q, 1))
   Ps.append((a, b))
   Ps.append((c, d))

from itertools import product

for (a, b), (c, d) in product(Ps, repeat=2):
   P = encode(a, b)
   Q = encode(c, d)
   if P == Q: continue
   G[P].append((Q, abs(c-a) + abs(d-b)))


def dijkstra(G, s):
   from heapq import heappop, heappush
   good = defaultdict(bool)
   dist = defaultdict(lambda: INF)
   dist[s] = 0
   Q = [(0, s)]
   while Q:
      dv, v = heappop(Q)
      if good[v]:
         continue
      good[v] = True
      for a, cost in G[v]:
         if good[a]:
            continue
         da = dv + cost
         if dist[a] > da:
            dist[a] = da
            heappush(Q, (da, a))
   return dist


dist = dijkstra(G, s=encode(0, 0))
ans = dist[encode(H-1, W-1)]
print(ans)