local n, k = io.read("*n", "*n")
local t = {}
local sum = 0
for i = 1, n do
  sum = sum + io.read("*n")
end
for i = 1, n do
  t[i] = io.read("*n")
end
for i = 1, n do
  z = io.read("*n")
  t[i] = t[i] - z
  sum = sum + z
end
table.sort(t)
for i = n, n + 1 - k, -1 do
  sum = sum + t[i]
end
sum = tostring(1LL * sum):gsub("LL", "")
print(sum)