fun harm(i:int, c:int):real =
    case evenP c of
        true => case c of
                    0 => 1.0
                  | _ => 1.0 * (1 div c) + harm(i, c+1)
     | false => case c of
                    0 => 1.0
                 | _ => -1.0 * (1 div c) + harm(1, c+1)