#include <cstdio>
#include <algorithm>

using namespace std; 

int INF=(1<<30),G,w,d[1002][5002],o,l,e,c,i,n,j; 
int main() 
{ 
	freopen("energii.in","r",stdin);
	freopen("energii.out","w",stdout);
	 scanf("%d%d",&n,&w);
     for (i=0;i<=n;i++) 
         for (j=1;j<=w;j++) 
         d[i][j]=INF; 
         
     for (i=1;i<=n;i++) 
     { 
       scanf("%d%d",&e,&c);
       for(j=e;j<=w;j++){
       		d[i][j]=d[i-1][j];
       		if(d[i-1][j-e]<INF)
       			d[i][j]=min(d[i-1][j-e]+c,d[i][j]);
       }
     } 
    if (d[n][w]==INF) printf("-1\n");
    else printf("%d\n",d[n][w]); 
    return 0; 
}