N=int(input())
N_mem=[]
for i in range(N):
    x,y=(int(x) for x in input().split())
    N_mem.append([999-y,x])

M=int(input())
M_mem=set()
for i in range(M):
    x,y=(int(x) for x in input().split())
    M_mem.add((999-y,x))

visited=[[False]*(10**3) for i in range(10**3)]

stack=[]
for i,j in N_mem:
    visited[i][j] = True
    stack.append([i,j])

next_move=[]
move=[[1,0],[-1,0],[0,1],[0,-1]]
ans=0
found=False
while stack:
    for i in stack:
        if tuple(i) in M_mem:
            found=True
            break
        for j in move:
            if 0 <= i[0]+j[0] < 10**3 and 0 <= i[1]+j[1] < 10*3 and visited[i[0]+j[0]][i[1]+j[1]] == False:
                visited[i[0]+j[0]][i[1]+j[1]] = True
                next_move.append([i[0]+j[0], i[1]+j[1]])
    
    if found:
        print(ans)
        exit()

    ans += 1
    stack, next_move = next_move, []