#include <cstdio>
#include <algorithm>
#include <string>

bool g(std::string const& s, std::string const& t) {
  return (std::search(s.begin(), s.end(), t.begin(), t.end()) != s.end());
}

char f(std::string const& s) {
  if (g(s, "-o--")) return true;
  if (g(s, "--o-")) return true;
  if (g(s, "-oo")) return true;
  if (g(s, "o-o")) return true;
  if (g(s, "oo-")) return true;
  if (g(s, "ooo")) return true;
  return false;
}

int main() {
  int t;
  scanf("%d", &t);

  while (t--) {
    size_t n;
    char buf[1024];
    scanf("%zu %s", &n, buf);
    std::string s = buf;
    puts(f(s)? "O": "X");
  }
}