#include <stdio.h>

typedef struct {
	int key, id;
} data;

void merge_sort(int n, data x[])
{
	static data y[5001] = {};
	if (n <= 1) return;
	merge_sort(n / 2, &(x[0]));
	merge_sort((n + 1) / 2, &(x[n/2]));
	
	int i, p, q;
	for (i = 0, p = 0, q = n / 2; i < n; i++) {
		if (p >= n / 2) y[i] = x[q++];
		else if (q >= n) y[i] = x[p++];
		else y[i] = (x[p].key < x[q].key)? x[p++]: x[q++];
	}
	for (i = 0; i < n; i++) x[i] = y[i];
}

void chmax(long long* a, long long b)
{
	if (*a < b) *a = b;
}

int main()
{
	int i, N, M, V[5001], W[5001];
	data d[5001];
	scanf("%d %d", &N, &M);
	for (i = 1; i <= N; i++) {
		scanf("%d %d", &(V[i]), &(W[i]));
		d[i-1].key = V[i];
		d[i-1].id = i;
	}
	merge_sort(N, d);
	
	int j, k;
	long long ans = 0, dp[5001] = {};
	for (i = N - 1; i >= 0; i--) {
		k = d[i].id;
		for (j = M - W[k]; j >= 0; j--) {
			chmax(&ans, V[k] * (dp[j] + V[k]));
			chmax(&(dp[j+W[k]]), dp[j] + V[k]);
		}
	}
	printf("%lld\n", ans);
	fflush(stdout);
	return 0;
}