#include <stdio.h>
#include <limits.h>
#include <algorithm>
FILE *f=fopen("energii.in","r");
FILE *g=fopen("energii.out","w");
using namespace std;
int G,W;
int co[10001],minc=INT_MAX;
bool x[5004];

struct energ{
	int e;
	int c;
};
energ a[1003];

int cmp(energ a,energ b){
	if(a.c<b.c)
		return 1;
	else 
		return 0;
}

int main(void){
	register int i,j;
	
	fscanf(f,"%d %d",&G,&W);
	for(i=1;i<=G;i++){
		fscanf(f,"%d %d",&a[i].e,&a[i].c);
	}
	fclose(f);
	
	sort(a+1,a+G+1,cmp);
	x[0]=1;
	for(i=1;i<=G;i++){
		for(j=W;j>=0;j--){
			if(x[j]){
				if(j+a[i].e>=W){
					//am gasit o posibila solutie
					if(co[j]+a[i].c<minc){
						minc=co[j]+a[i].c;
					}	
				}
				else if(j+a[i].e<W){
					if(x[j+a[i].e]){
						if(co[j+a[i].e]>co[j]+a[i].c){
							co[j+a[i].e]=co[j]+a[i].c;
						}
					}
					else{
						co[j+a[i].e]=co[j]+a[i].c;
						x[j+a[i].e]=true;					
					}
				}
			}
		}
	}
	if(minc==INT_MAX)
		minc=-1;
	fprintf(g,"%d",minc);
	return 0;
}