var g,w,e,c,max,i,k:longint;
    v:array[0..100001]of longint;
begin
assign(input,'energii.in');
reset(input);
read(g,w);
read(e,c);
v[e]:=c;
max:=e;
for i:=2 to g do
begin
     read(e,c);
     for k:=max downto 1 do
         if(v[k]>0)and((v[k]+c<v[k+e])or(v[k+e]=0))then
            v[k+e]:=v[k]+c;
     if(v[e]>c)or(v[e]=0)then
     v[e]:=c;
     max:=max+e;
end;
close(input);
assign(output,'energii.out');
rewrite(output);
for i:=w to max do
    if(v[i]<>0)then
    break;
write(v[i]);
close(output);
end.