#include <cstdio>
#define POS_BUN 1
#define POS_REA -1
#define NMax 100000

long n, max, cost[NMax], ener[NMax];
long a[NMax], b[NMax], pos[NMax];

int main()
{
	long i, j, mx, ex;
	FILE *fin = fopen( "energii.in", "rt" );
	fscanf( fin, "%d %d", &n, &max );
	for (i=0; i<n; i++)
		fscanf( fin, "%d %d", &ener[i], &cost[i] );

	a[n-1] = cost[n-1];
	b[n-1] = ener[n-1];
	if ( b[n-1] == max )
		pos[n-1] = n-1;
	else
		pos[n-1] = POS_REA;

	for (i=n-2; i>=0; i--)
	{
		mx = ex = 0;
		for (j=i+1; j<n; j++)
			if ( ener[i] + b[j] <= max )
				if ( cost[i]+a[j] > mx )
				{
					mx = cost[i] + a[j];
					ex = b[j];
				}

		a[i] = mx;
		b[i] = ener[i] + ex;		
		
		if ( b[i] == max )
			pos[i] = i;
		else pos[i] = POS_REA;
	}

	FILE *fout = fopen( "energii.out", "wt" );
	for (i=0; i<n; i++)
	{
		if ( pos[i] != POS_REA )
		{
			fprintf( fout, "%d", a[i] );
			fprintf( fout, "\n" );
			return 0;
		}
	}
	return 0;
}