#include<stdio.h>
#include<algorithm>
using namespace std;
long n,s,i,j,suma;
struct energii
{
	int x,y;
};
energii a[1001];
int cmp(energii a,energii b)
{
	return a.x>b.x;
}
int main()
{
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	scanf("%ld %ld",&n,&s);
	for (i=1;i<=n;i++)
		scanf("%ld %ld",&a[i].x,&a[i].y);
	sort(a+1,a+n+1,cmp);
	i=1;
	while (s-a[i].x>0)
		i++;
	for (j=1;j<=i;j++)
		suma+=a[i].y;
	printf("%ld",suma);
}