ans = 0
x = int(input())
y = int(input())
l = int(input())
if x != 0:
    if y < 0:
        ans += 2
    else:
        ans +=1
x = (x**2)**0.5
y = (y**2)**0.5
ans += ((x+l-1)//l+(y+l-1)//l)
print(ans)