#!/usr/bin/python3

import math

with open('energii.in', 'r') as fin:
    generatoare = int(fin.readline())
    energie_necesara = int(fin.readline())
    cost_total = [math.inf for i in range(energie_necesara+1)]
    cost_total[0] = 0
    for i in range(generatoare):
        energie, cost = (int(x) for x in fin.readline().split())
        for tinta in range(energie_necesara, energie-1, -1):
            cost_nou = cost_total[tinta - energie] + cost
            cost_total[tinta] = min(cost_total[tinta], cost_nou)

with open('energii.out', 'w') as fout:
    raspuns = cost_total[energie_necesara]
    if raspuns == math.inf:
        raspuns = -1
    print(raspuns, file=fout)