#include<stdio.h>  
   #include <limits.h>	
   int main()  
   { int n,g,i,e,c,v[16000];   
     
	   freopen("energii.in","r",stdin);  
       freopen("energii.out","w",stdout);  
       for(i=1;i<=16000;i++) v[i]=1000000000;
       v[0]=0;  
       scanf("%d%d",&n,&g);  
       for(;n;n--)  
       {  
           scanf("%d%d",&e,&c);  
           for(i=g-1;i>=0;i--)  
               if ((i+e<=g)  && (v[i+e]>v[i]+c))
                  v[i+e]=v[i]+c;    
               else  
                  if(v[g]>v[i]+c) v[g]=v[i]+c;  
       }
	   
       if(v[g]==1000000000) v[g]=-1;  
		printf("%d\n",v[g]);  
	   
       return 0;  
    }