#! /usr/bin/env ruby

n = gets.chomp.to_i
Item = Struct.new(:a, :b)
its = Array.new(n)
n.times do |i|
  a, b = gets.split.map(&:to_i)
  its[i] = Item.new(a, b)
end
its.sort! { |l, r| r.b <=> l.b }
dp = Array.new(n + 1) { Array.new(n + 1, 1234567899876543210) }
dp[0][0] = 0
n.times do |i|
  (0..i).each do |j|
    dp[i + 1][j] = [dp[i + 1][j], dp[i][j] + its[i].a + its[i].b * (i - j)].min
    dp[i + 1][j + 1] = [dp[i + 1][j + 1], dp[i][j]].min
  end
end
puts dp[n][n / 3]