x, y, r = io.read("*n", "*n", "*n")
cmd = 0
if(x == 0) then
    if(y < 0) then cmd = 2 end
elseif(y == 0) then
    cmd = 1
else
    if(0 < y) then cmd = 1 else cmd = 2 end
end
x, y = math.abs(x), math.abs(y)
cmd = cmd + math.floor(x / r) + math.floor(y / r)
if(0 < x % r) then cmd = cmd + 1 end
if(0 < y % r) then cmd = cmd + 1 end
print(cmd)