local n, m = io.read("*n", "*n")
local a = {}
for i = 1, n do
  a[i] = io.read("*n")
end
table.sort(a)
local v = 0LL
for i = 2, m do
  v = v + 1LL * (a[i] - a[i - 1]) * (a[i] - a[i - 1])
end
local ans = v
for i = m + 1, n do
  v = v - 1LL * (a[i - m + 1] - a[i - m]) * (a[i - m + 1] - a[i - m])
  v = v + 1LL * (a[i] - a[i - 1]) * (a[i] - a[i - 1])
  if v < ans then ans = v end
end
ans = tostring(ans):gsub("LL", "")
print(ans)