N,M = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(N)]
A = [0]+sorted(A,key=lambda x:x[0],reverse=True)
INFTY = 10**10
dp = [[-INFTY for _ in range(M+1)] for _ in range(N+1)]
for j in range(1,M+1):
    if j>=A[1][1]:
        dp[1][j] = A[1][0]
for i in range(2,N+1):
    for j in range(1,M+1):
        dp[i][j] = dp[i-1][j]
        if j>=A[i][1]:
            dp[i][j] = max(dp[i][j],dp[i-1][j-A[i][1]]+A[i][0])
ans = 0
for i in range(1,N+1):
    ans = max(ans,A[i][0]*dp[i][M])
print(ans)