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

var f1,f2:text;
    eng,cost,i,j,g,w:longint;
    a:array[1..1010] of gener;
    aux:gener;
    v:array[1..100000] 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
        begin
                read(f1,a[i].e,a[i].c);
                eng:=eng+a[i].e;
                cost:=cost+a[i].c;
        end;
        for i:=1 to g-1 do
                for j:=i+1 to g do
                        if a[i].c<a[j].c then
                        begin
                                aux:=a[i];
                                a[i]:=a[j];
                                a[j]:=aux;
                        end;
        for i:=1 to w do
                v[i]:=maxlongint;
        for i:=1 to g do
                for j:=0 to w do
                        if v[j]<>maxlongint then
                                if v[j]+a[i].c<v[j+a[i].e] then
                                        v[j+a[i].e]:=v[j]+a[i].c;
        writeln(f2,v[w]);
        close(f1);
        close(f2);
end.