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

var f1,f2:text;
    i,j,g,w,f,p:longint;
    a:array[1..1010] of gener;
    aux: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 downto a[i].e do
                                if pos[j-a[i].e]=1 then
                                begin
                                        pos[j]:=1;
                                        if (pc[j-a[i].e]+a[i].c<pc[j])or(pc[j]=0) then
                                                pc[j]:=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.