The tour operator did not sell n (n < 15) vouchers to mountain-ski resort because of the great frost. The terms of vouchers validity is already come. To reduce the losses, it was decided from the February 1, that all the vouchers for which remained d_k (d_k ≤ 30) days, to sell for minimal cost – for с_k (с_k ≤ 100) UAH for a day only for that days, which remained from the sale day (k = 1..n).

   What is the largest amount of income can get the travel company selling these vouchers, if one voucher can be sold only in one day?

   Input

   The first line contains the number of vouchers n. Each of the next n lines contains two numbers - the number of days d_k left and the cost of each day c_k.

   Output

   The maximum amount of income.