#include <stdio.h>

FILE *f,*s;

int g,w,x,y,i,j,sum,max,v[1000000];

int main()
{
	f=fopen("energii.in","r");
	s=fopen("energii.out","w");
	
	fscanf(f,"%d\n%d\n",&g,&w);
	
	for(i=1;i<=g;i++)
	{
		fscanf(f,"%d %d\n",&x,&y);
		
		v[x]+=y;
		
		sum+=x;
		
		for(j=1;j<=sum;j++)
		{
			if(v[j]>0)
				v[j+x]+=y;
		}	
	}		
	
	if(sum<w)
		fprintf(s,"-1\n");
	else
	{
		for(i=w;i<=sum;i++)
		{
			if(v[i]!=0)
			{
				fprintf(s,"%d\n",v[i]);
				break;
			}	
		}	
	}			
	
	fclose(s);
	
	return 0;
}