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문제

Farmer John is running out of supplies and needs to purchase H (1 <= H <= 50,000) pounds of hay for his cows.

He knows N (1 <= N <= 100) hay suppliers conveniently numbered 1..N. Supplier i sells packages that contain P_i (1 <= P_i <= 5,000) pounds of hay at a cost of C_i (1 <= C_i <= 5,000) dollars. Each supplier has an unlimited number of packages available, and the packages must be bought whole.

Help FJ by finding the minimum cost necessary to purchase at least H pounds of hay.

입력

  • Line 1: Two space-separated integers: N and H
  • Lines 2..N+1: Line i+1 contains two space-separated integers: P_i and C_i

 

출력

  • Line 1: A single integer representing the minimum cost FJ needs to pay to obtain at least H pounds of hay.

 

예제 입력

2 15
3 2
5 3

예제 출력

9

힌트

FJ can buy three packages from the second supplier for a total cost of 9.