n = gets.to_i
a = (1..n).map { gets.split.map &:to_i }.sort_by { -_2 }

I = 10**18
dp = [I] * (n + 1)
dp[0] = 0
(0...n).each do |t|
	dp =
		(0..n).map do |i|
			[dp[i] + a[t][0] + a[t][1] * (t - i), dp[i - 1] || I].min
		end
end
p dp[n / 3]