type    generator=record
                   e,cost:int64;
                   end;
        tablou=array [0..1010]of generator;
var t:tablou;
    rez:array[0..5010]of int64;
    i,j,k,m,n:longint;
    f,g:text;
begin
assign(f,'energii.in');
assign(g,'energii.out');
reset(f);
rewrite(g);
read(f,n);
read(f,m);
for i:=1 to n do
 read(f,t[i].e,t[i].cost);
for i:=1 to m do
  for j:=1 to n do
   if i-t[j].e>=0 then begin
                  if (rez[t[j].e]=0)then rez[t[j].e]:=t[j].cost
                  else if rez[i]>(rez[i-t[j].e]+t[j].cost)then rez[i]:=rez[i-t[j].e]+t[j].cost;
                  end;

write(g,rez[m]);
close(f);
close(g);
end.