type gener=record
           e,c:longint;
     end;

var f1,f2:text;
    i,j,g,w,f:longint;
    a:array[1..1010] of gener;
    pos,pc:array[0..10000] of longint;
begin
        assign(f1,'energii.in');
        reset(f1);
        assign(f2,'energii.out');
        rewrite(f2);
        read(f1,g,w);
        for i:=1 to g do
                read(f1,a[i].e,a[i].c);
        pos[0]:=1;
        for i:=1 to g do
                if (a[i].e>=w)and((a[i].c<pc[w])or(pc[w]=0)) then
                        pc[w]:=a[i].c
                else if a[i].e<w then
                        for j:=w+a[i].e downto a[i].e do
                                if pos[j-a[i].e]=1 then
                                begin
                                        f:=j;
                                        if j>w then
                                                f:=w;
                                        pos[f]:=1;
                                        if (pc[j-a[i].e]+a[i].c<pc[f])or(pc[f]=0) then
                                                pc[f]:=pc[j-a[i].e]+a[i].c;
                                end;
        if pc[w]=0 then
                writeln(f2,-1)
        else writeln(f2,pc[w]);
        close(f1);
        close(f2);
end.