x = int(input())
y = int(input())
l = int(input())

x = abs(x)

if y >= 0:
    if x == 0:
        ans = (y+l-1)//l
    else:
        ans = (y+l-1)//l+1+(x+l-1)//l
else:
    ans = 1+(x+l-1)//l+1+(-y+l-1)//l

print(ans)