H,W,N=map(int,input().split())
from collections import defaultdict,deque
G=defaultdict(defaultdict)
C=defaultdict(int)
I=[]
O=[]
G[(1,1)][(H,W)]=H-1+W-1
for _ in range(N):
    a,b,c,d=map(int,input().split())
    G[(1,1)][(a,b)]=a-1+b-1
    G[(1,1)][(c,d)]=c-1+d-1
    G[(a,b)][(c,d)]=1
    G[(a,b)][(H,W)]=H-a+H-b
    G[(c,d)][(H,W)]=H-c+W-d
    C[(a,b)]=1<<60
    C[(c,d)]=1<<60
    I.append((a,b))
    O.append((c,d))
for c,d in O:
    for a,b in I:
        G[(c,d)][(a,b)]=abs(c-a)+abs(d-b)
        G[(a,b)][(c,d)]=abs(c-a)+abs(d-b)
C[(H,W)]=1<<60
C[(1,1)]=0
Q=deque()
Q.append((1,1))
while Q:
    a,b=Q.popleft()
    for c,d in G[(a,b)].keys():
        tmp=C[(a,b)]+G[(a,b)][(c,d)]
        if tmp<C[(c,d)]:
            C[(c,d)]=tmp
            Q.append((c,d))
print(C[(H,W)])