program energii;
var n,i,j,p,ct: longint;
e,c: array[1..100{1001}] of longint;
cm:array[0..100{5001}] of longint;
f: text;
const g=2000000000;
begin
     assign(f,'energii.in');
     reset(f);
     readln(f,n);
     readln(f,p);
     for i:=1 to n do
         readln(f,e[i],c[i]);
     for i:=1 to p do
         cm[i]:=g;
     ct:=g;
     cm[0]:=0;
     for i:=1 to n do
     for j:=p-1 downto 0 do
         if j+e[i]<p then
         begin
              if cm[j+e[i]]>cm[j]+c[i] then
              cm[j+e[i]]:=cm[j]+c[i];
         end else
             if cm[j]+c[i]<ct then
                ct:=cm[j]+c[i];
     assign(f,'energii.out');
     rewrite(f);
     if ct<>g then write(f,ct) else write(f,-1);
     close(f);
end.