H,W,N=map(int,input().split())
dic={}
dic[(1,1)]=0
dic[(H,W)]=1
num=2
pos=[(1,1),(H,W)]
abcd=[]
for i in range(N):
  a,b,c,d=map(int,input().split())
  if (a,b) not in dic:
    dic[(a,b)]=num
    pos.append((a,b))
    num+=1
  if (c,d) not in dic:
    dic[(c,d)]=num
    pos.append((c,d))
    num+=1
  abcd.append([a,b,c,d])

M=num
edge=[[] for i in range(M)]
for a,b,c,d in abcd:
  edge[dic[(a,b)]].append((dic[c,d],1))

for i in range(M):
  for j in range(M):
    xi,yi=pos[i]
    xj,yj=pos[j]
    edge[i].append([j,abs(xi-xj)+abs(yi-yj)])

from heapq import heappush, heappop
INF=10**18
def dijkstra(start,n):
  dist=[INF]*n
  hq=[(0,start)]
  dist[start]=0
  seen=[False]*n
  while hq:
    w,v=heappop(hq)
    if dist[v]<w:
      continue
    seen[v]=True
    for to,cost in edge[v]:
      if seen[to]==False and dist[v]+cost<dist[to]:
        dist[to]=dist[v]+cost
        heappush(hq,(dist[to],to))
  return dist

print(dijkstra(0,M)[1])