var n,m,i,j,s,h:longint;
    a,b:array[0..10000] of longint;
begin
   read(n,m);
    for i:=1 to n do
        read(a[i]);
    for i:=1 to n do
        read(b[i]);
    for i:=1 to n-1 do
        for j:=i+1 to n do
        if b[j]>b[i] then        
        begin
            h:=b[i];b[i]:=b[j];b[j]:=h;
            h:=a[i];a[i]:=a[j];a[j]:=h;
        end else if (b[j]=b[i]) and (a[j]>a[i]) then 
        begin
            h:=b[i];b[i]:=b[j];b[j]:=h;
            h:=a[i];a[i]:=a[j];a[j]:=h;
        end;
    j:=m;
    for i:=1 to n do
    begin
        inc(s,a[i]+b[i]*(j-1));
        dec(j);
        if j=0 then break;
    end;
    write(s);
end.