#include<stdio.h>  
long g,w,i,nr,max = 2000000000,v[15001],cg[1001],eg[1001];  
 int main()  
 {  
     freopen("energii.in","rt",stdin);  
     freopen("energii.out","wt",stdout);  
     scanf("%ld%ld",&g,&w);  
     for(i=1;i<=g;i++)  
         scanf("%ld%ld",&eg[i],&cg[i]);  
  
     for(i=1;i<=w+10001;i++)  
         v[i] = 2000000000;  
  
     for( nr = 1; nr <= g; nr++)  
         for( i = w; i >= 0  ; i--)  
             if(v[i]<2000000000)  
                 {  
                 if(i+eg[nr]>=w && v[i]+cg[nr] <max) max=v[i]+cg[nr];  
                 else  
                     if(v[i+eg[nr]]>v[i]+cg[nr])  
                         v[i+eg[nr]] = v[i]+cg[nr];  
                 }  
  
     if(max<2000000000) printf("%ld",max);  
     else printf("-1\n");  
  
  
     return 0;  
 }