local mmi, mma = math.min, math.max
local n = io.read("*n")
local a, b = {}, {}
local idx = {}
for i = 1, n do
  a[i], b[i] = io.read("*n", "*n")
  idx[i] = i
end
table.sort(idx, function(x, y) return b[x] > b[y] end)
local trim = math.floor(n / 3)
local lim = n - trim
local t = {}
local inf = 1000000007 * 1000000007
for i = 1, lim do
  t[i] = inf
end
for i_ = 1, n do
  local i = idx[i_]
  local ai, bi = a[i], b[i]
  for j = lim - 1, 0, -1 do
    local src = j == 0 and 0 or t[j]
    local cost = ai + bi * j
    t[j + 1] = mmi(t[j + 1], src + cost)
  end
  -- print(table.concat(t, " "))
end
print(t[lim])