Problem:
Score : 500 points

Problem Statement

Snuke, who loves animals, built a zoo.

There are N animals in this zoo. They are conveniently numbered 1 through N, and arranged in a circle.
The animal numbered i (2≤i≤N-1) is adjacent to the animals numbered i-1 and i+1. Also, the animal numbered 1 is adjacent to the animals numbered 2 and N, and the animal numbered N is adjacent to the animals numbered N-1 and 1.

There are two kinds of animals in this zoo: honest sheep that only speak the truth, and lying wolves that only tell lies.

Snuke cannot tell the difference between these two species, and asked each animal the following question: "Are your neighbors of the same species?" The animal numbered i answered s_i. Here, if s_i is o, the animal said that the two neighboring animals are of the same species, and if s_i is x, the animal said that the two neighboring animals are of different species.

More formally, a sheep answered o if the two neighboring animals are both sheep or both wolves, and answered x otherwise.
Similarly, a wolf answered x if the two neighboring animals are both sheep or both wolves, and answered o otherwise.

Snuke is wondering whether there is a valid assignment of species to the animals that is consistent with these responses. If there is such an assignment, show one such assignment. Otherwise, print -1.

Constraints

3 ≤ N ≤ 10^{5}

s is a string of length N consisting of o and x.

Input

The input is given from Standard Input in the following format:

N
s

Output

If there does not exist an valid assignment that is consistent with s, print -1.
Otherwise, print an string t in the following format. The output is considered correct if the assignment described by t is consistent with s.

t is a string of length N consisting of S and W.

If t_i is S, it indicates that the animal numbered i is a sheep. If t_i is W, it indicates that the animal numbered i is a wolf.

Sample Input 1

6
ooxoox

Sample Output 1

SSSWWS

For example, if the animals numbered 1, 2, 3, 4, 5 and 6 are respectively a sheep, sheep, sheep, wolf, wolf, and sheep, it is consistent with their responses. Besides, there is another valid assignment of species: a wolf, sheep, wolf, sheep, wolf and wolf.

Let us remind you: if the neiboring animals are of the same species, a sheep answers o and a wolf answers x. If the neiboring animals are of different species, a sheep answers x and a wolf answers o.

Sample Input 2

3
oox

Sample Output 2

-1

Print -1 if there is no valid assignment of species.

Sample Input 3

10
oxooxoxoox

Sample Output 3

SSWWSSSWWS

Solution in Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

import Data.Array.Unboxed
import Data.Bool
import qualified Data.ByteString.Char8  as C
import Data.List
import Data.Maybe

main = sol <$> getn <*> gets >>= put

getn = fst . fromJust . C.readInt <$> C.getLine

gets = C.filter ((||) <$> ('o' ==) <*> ('x' ==)) <$> C.getLine

put = putStrLn . (flip bool "-1" <*> null)

sol n s = maybe "-1" init $ find ((==) <$> head <*> last) [ss,sw,ws,ww]
  where
  a = listArray (0,n) $ (=='o') <$> C.last s:C.unpack s :: UArray Int Bool
  ss = 'S':unfoldr step ('S','S',1)
  sw = 'W':unfoldr step ('S','W',1)
  ws = 'S':unfoldr step ('W','S',1)
  ww = 'W':unfoldr step ('W','W',1)
  step ('S','S',i) = if i<=n
    then Just (nxt, ('S',nxt,i+1))
    else Nothing
    where
    nxt = bool 'W' 'S' (a!i)
  step ('S','W',i) = if i<=n 
    then Just (nxt, ('W',nxt,i+1))
    else Nothing
    where
    nxt = bool 'S' 'W' (a!i)
  step ('W','S',i) = if i<=n 
    then Just (nxt, ('S',nxt,i+1))
    else Nothing
    where
    nxt = bool 'S' 'W' (a!i)
  step ('W','W',i) = if i<=n
    then Just (nxt, ('W',nxt,i+1))
    else Nothing
    where
    nxt = bool 'W' 'S' (a!i)