from collections import deque
def bfs(s):
    dq=deque()
    dq.append([s,0])
    high=[10**9 for _ in range(H*W)]
    high[s]=0
    while len(dq)!=0:
        p,h=dq.popleft()
        for e in edge[p]:
            if  high[e]==10**9:
                dq.append([e,h+1])
                high[e]=h+1
    return high

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

H,W,N=map(int,input().split())
edge=[[] for _ in range(H*W)]
for i in range(H-1):
    for j in range(W):
        edge[csv(i,j)].append(csv(i+1,j))
        edge[csv(i+1,j)].append(csv(i,j))
for i in range(H):
    for j in range(W-1):
        edge[csv(i,j)].append(csv(i,j+1))
        edge[csv(i,j+1)].append(csv(i,j))
for i in range(N):
    a,b,c,d=map(int,input().split())
    edge[csv(a-1,b-1)].append(csv(c-1,d-1))
dist=bfs(0)
print(dist[-1])