let rec power ( * ) e m n =
  if n <= 0 then e
  else power ( * ) (if n land 1 = 0 then e else m * e) (m * m) (n lsr 1)

let m = 1000000007
let ( +^ ) x y = (x + y) mod m
let ( -^ ) x y = x +^ (m - y)
let ( *^ ) x y = (x * y) mod m
let ( /^ ) x y = power ( *^ ) x y (m - 2)

let () = Scanf.scanf "%d %s" @@ fun k s ->
  (* comb.(i) = (|S| - 1 + i)C(|S| - 1) *)
  let comb = Array.make (k + 1) 0 in
  comb.(0) <- 1;
  for i = 1 to k do
    comb.(i) <- (String.length s - 1 + i) *^ comb.(i - 1) /^ i
  done;
  Printf.printf "%d\n" @@
  Array.fold_left ( +^ ) 0 @@
  Array.init (k + 1) @@ fun i ->
    power ( *^ ) (power ( *^ ) comb.(k - i) 25 (k - i)) 26 i
