import algorithm, math, strutils, sequtils, tables, macros

let read* = iterator: string {.closure.} =
  while true: (for s in stdin.readLine.split: yield s)

template input*(T: static[typedesc]): untyped = 
  when T is int: read().parseInt
  elif T is float: read().parseFloat
  elif T is string: read()

macro dump*(arg: varargs[untyped]): untyped =
  result = newNimNode(nnkStmtList)
  for x in arg:
    let name = toStrLit(x)
    result.add(quote do: stderr.write `name`, " = " , `x`, ", ")
  result.add(quote do: stderr.write "\n")

proc check(S: string): bool =
  return S.contains("--o-") or S.contains("-o--") or S.contains("-oo") or
  S.contains("oo-") or S.contains("o-o") or S.contains("ooo")

let T = input(int)
for _ in 1 .. T:
  let _ = input(int)
  let S = input(string)
  if check(S):
    echo "O"
  else:
    echo "X"