import io
import sys
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, accumulate
from heapq import heappush, heappop
from bisect import bisect_right, bisect_left
from math import gcd
import math

_INPUT = """\
6
3 3 1
1 2 3 2
5 4 2
2 4 1 2
4 4 2 1
10 10 5
4 5 3 3
4 6 6 10
8 8 10 5
9 5 3 1
9 3 3 4
"""
def Dijkstra(G,s):
  done=[False]*len(G)
  inf=10**20
  C=[inf]*len(G)
  C[s]=0
  h=[]
  heappush(h,(0,s))
  while h:
    x,y=heappop(h)
    if done[y]:
      continue
    done[y]=True
    for v in G[y]:
      if C[v[1]]>C[y]+v[0]:
        C[v[1]]=C[y]+v[0]
        heappush(h,(C[v[1]],v[1]))
  return C

def input():
  return sys.stdin.readline()[:-1]

def solve(test):
  H,W,N=map(int, input().split())
  warp=[list(map(int, input().split())) for _ in range(N)]
  G=[[] for _ in range(2*N+2)]
  z=[]
  for i in range(N):
    a,b,c,d=warp[i]
    G[2*i].append((1,2*i+1))
    z.append((a,b))
    z.append((c,d))
  z.append((1,1))
  z.append((H,W))
  for i in range(2*N+2):
    a,b=z[i]
    for j in range(i+1,2*N+2):
      c,d=z[j]
      G[i].append((abs(a-c)+abs(b-d),j))
      G[j].append((abs(a-c)+abs(b-d),i))
  print(Dijkstra(G,2*N)[2*N+1])

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)