const M=(1 shl 14);
var i,j,gen,min,w:longint;
    e,c:array[1..10000] of longint;
    v:array [0..M] of longint;
    f,g:text;
begin
    assign(f,'energii.in');
    assign(g,'energii.out');
    reset(f);
    rewrite(g);
    readln(f,gen);
    readln(f,w);
    for i:=1 to gen do
        readln(f,e[i],c[i]);
    for i:=1 to M do v[i]:=maxlongint;
    for i:=1 to gen do
       begin
         for j:=w downto 0 do
             if (v[j]<>maxlongint) and (v[j]+c[i]<v[j+e[i]]) then
                 v[j+e[i]]:=v[j]+c[i];
       end;
    min:=maxlongint;
    for i:=w to M do
         if (v[i]<min) then
            min:=v[i];
    if min=maxlongint then writeln(g,-1)
    else writeln(g,min);
    close(g);
end.