input = open("energii.in", "r")
output = open("energii.out","w")

n = int(input.readline())
w = int(input.readline())

cost = [50000001]*(w+1)

for i in range(0,n):
    x = input.readline().replace("\n","").split(" ")
    x[0]=int(x[0])
    x[1]=int(x[1])
    
    for j in range(w, x[0], -1):
        cost[j] = min(cost[j], cost[j - x[0]] + x[1])
    
    for j in range(1,x[0]+1):
        cost[j] = min(cost[j], x[1])
 
if cost[w] == 50000001 :
    output.write("-1")
else:
    output.write(str(cost[w]))

input.close()
output.close()