#include<stdio.h>

int e[1002],c[1002],v[2004],a[2004],i,k,j,g,w,min,h,x,y;

int main () {
    FILE *f = fopen("energii.in","r");
    FILE *t = fopen("energii.out","w");
    
    fscanf(f,"%d %d",&g,&w);
    for(i=1;i<=g;i++)
                     fscanf(f,"%d %d",&e[i],&c[i]);
    k=0;
    for(i=1;i<=g;i++){
	    v[++k]=e[i];
	    x=v[k];
	    a[k]=c[i];
	    y=a[k];
	    for(j=i+1;j<=g;j++){
		       v[++k]=x+e[j];
		       x=v[k];
		       a[k]=y+c[j];
		       y=a[k];
                       }
                       }
     min=10001;
     for(i=1;i<=k;i++)
                      if(v[i]>=w&&a[i]<min)
					   min=a[i];
    h=-1;
    if(min==10001)
		  fprintf(t,"-1");
	 else
		  fprintf(t,"%d",min);
    
    
    
    fclose(f);
    fclose(t);
return 0;
}