var
  P,K,M,a,a1,a2 : array [1..100] of longint;
  i,n,x,kp,kk,km,j,x1,x2,sum1,sum2 : longint;
  s : string;
begin
  readln(n,x);
  for i:=1 to n do
    read(a[i]);
  readln;
  readln(s);
  for i:=1 to length(s) do
    if pos('P',s[i])<>0 then begin
      kp:=kp+1;
      P[i]:=a[i];
    end;
  for i:=1 to length(s) do
    if pos('K',s[i])<>0 then begin
      kk:=kk+1;
      K[i]:=a[i];
    end;
  for i:=1 to length(s) do
    if pos('M',s[i])<>0 then begin
      km:=km+1;
      M[i]:=a[i];
    end;
  if kk=0 then begin
    writeln('NO');
    exit;
  end;
  if (km=0) and (kp=0) then begin
    writeln('NO');
    exit;
  end;
  for i:=1 to n-km-1 do
    begin
      a1[i]:=K[i];
      a1[i+1]:=P[i];
    end;
  for i:=1 to n-kp-1 do
    begin
      a2[i]:=K[i];
      a2[i+1]:=M[i];
    end;
  for i:=1 to n-km-1 do
    for j:=1 to n-km-i do
      if a1[j]<a1[j+1] then
        begin
          x1:=a1[j];
          a1[j]:=a1[j+1];
          a1[j+1]:=x1;
        end;
  for i:=1 to x do
    sum1:=sum1+a1[j];
  for i:=1 to n-kp-1 do
    for j:=1 to n-kp-i do
      if a2[j]<a2[j+1] then
        begin
          x2:=a2[j];
          a2[j]:=a2[j+1];
          a2[j+1]:=x2;
        end;
  for i:=1 to x do
    sum2:=sum2+a[j];
  if sum1>sum2 then writeln(sum1)
  else writeln(sum2);
end.