N, M = map(int, input().split())
VW = [tuple(map(int, input().split())) for _ in range(N)]
DP = [[-1] * (M + 1) for _ in range(N + 1)]
DP[0][0] = 0

def chmax(DP,i,v):
    if DP[i] < v: DP[i] = v
def chmin(DP,i,v):
    if DP[i] > v: DP[i] = v

VW.sort(key=lambda x: x[0], reverse=True)

for i in range(N):
    for j in range(M + 1):
        if DP[i][j] == -1:
            continue
        # 不採用
        chmax(DP[i + 1], j, DP[i][j])
        v, w = VW[i]
        # 採用
        if j + w <= M:
            chmax(DP[i + 1], j + w, DP[i][j] + v)
ansl = []
for i in range(1, N + 1):
    min_beauty = VW[i - 1][0]
    total_beauty = max(DP[i])
    ansl.append(min_beauty * total_beauty)

ans = max(ansl)
print(ans)