def f(n, m):
    return n * 5005 + m

N, M = map(int, input().split())
D = []
for i in range(N):
    V, W = map(int, input().split())
    D.append( (V, W) )
D.sort(reverse=True)

inf = 10 ** 18
dp = [-inf] * (5005 * 5005)
premax = [-inf] * (M + 1)
dp[0] = 0
premax[0] = 0
for i in range(N):
    Acmax = [-inf] * (M + 1)
    V, W = D[i]
    for j in range(M + 1):
        if j - W >= 0:
            dp[f(i + 1, j)] = premax[j - W] + V
        Acmax[j] = max(dp[f(i + 1, j)], premax[j])
    premax, Acmax = Acmax, premax

ans = 0
for i in range(N):
    for j in range(M + 1):
        ans = max(ans, dp[f(i + 1, j)] * D[i][0])
print(ans)