x = int(input())
y = int(input())
l = int(input())
if x == 0 and y == 0:
    print(0)
    exit()
if y >= 0:
    if x == 0:
        ans = -(-y//l)
    else:
        ans = -(-y//l) -(-abs(x)//l) + 1
else:
    ans = -(-abs(y)//l) -(-abs(x)//l) + 2
print(ans)