def main ():
    input = open("energii.in", "r")
    output = open("energii.out","w")
    toInt = lambda a : [int(a[0]), int(a[1])]
    n, w = int(input.readline()), int(input.readline())
    cost = [50000001]*(w+1)
    i = 0
    while i<n:
        x = toInt(input.readline().replace("\n","").split(" "))
        
        j = w
        while j < x[0]:
            cost[j] = min(cost[j], cost[j - x[0]] + x[1])
            j -= 1
        
        j=1
        while j <= x[0]:
            cost[j] = min(cost[j], x[1])
            j += 1
        
        i +=1
    
    output.write("-1") if cost[w] == 50000001 else output.write(str(cost[w]))

    input.close()
    output.close()

main()