n,m=map(int,input().split())
jue=[list(map(int,input().split())) for i in range(n)]
jue.sort(reverse=True)

dp=[[-1]*(m+1) for i in range(n+1)]
dp[0][0]=0
ans=0

for i in range(n):
    for j in range(m):
        if dp[i][j] == -1:
            continue
        if j+jue[i][1] <= m:
            dp[i+1][j+jue[i][1]] = max(dp[i][j]+jue[i][0],dp[i+1][j+jue[i][1]])
            ans = max(ans,(dp[i][j]+jue[i][0]) * jue[i][0])
        dp[i+1][j] = max(dp[i][j],dp[i+1][j])
        
print(ans)