x, y, l = int(input()), int(input()), int(input())
def count(x, y, l):
    cnt=0
    if x!=0:
        cnt+=1
    if y<0:
        cnt+-2
    if x==0 and y<0:
        cnt+=2
    cnt+=abs(x)//l
    if abs(x)%l>0:cnt+=1
    cnt+=abs(y)//l
    if abs(y)%l>0:cnt+=1
    return cnt
print(count(x, y, l))