fin = open("rucsac.in","r")
fout = open("rucsac.out","w")

N = int(fin.readline())
v = []
G = int(fin.readline())

for i in range(N):
    w = int(fin.readline())
    p = int(fin.readline())
    v.append([p, w])

v.sort(reverse=True)

Pmax = 0

for i in range(N):
    if v[i][1] <= G:
        Pmax = Pmax + v[i][0]
        G = G - v[i][1]


fout.write(str(Pmax))
fin.close()
fout.close()