#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(int &x){
  int k;
  int m=0;
  x=0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m=1;
      break;
    }
    if('0'<=k&&k<='9'){
      x=k-'0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k<'0'||k>'9'){
      break;
    }
    x=x*10+k-'0';
  }
  if(m){
    x=-x;
  }
}
inline void rd(char &c){
  int i;
  for(;;){
    i = my_getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c = i;
}
inline int rd(char c[]){
  int i;
  int sz = 0;
  for(;;){
    i = my_getchar_unlocked();
    if(i!=' '&&i!='\n'&&i!='\r'&&i!='\t'&&i!=EOF){
      break;
    }
  }
  c[sz++] = i;
  for(;;){
    i = my_getchar_unlocked();
    if(i==' '||i=='\n'||i=='\r'||i=='\t'||i==EOF){
      break;
    }
    c[sz++] = i;
  }
  c[sz]='\0';
  return sz;
}
inline int rd_int(void){
  int x;
  rd(x);
  return x;
}
struct MY_WRITER{
  char buf[1048576];
  int s;
  int e;
  MY_WRITER(){
    s = 0;
    e = 1048576;
  }
  ~MY_WRITER(){
    if(s){
      fwrite_unlocked(buf, 1, s, stdout);
    }
  }
}
;
MY_WRITER MY_WRITER_VAR;
void my_putchar_unlocked(int a){
  if(MY_WRITER_VAR.s == MY_WRITER_VAR.e){
    fwrite_unlocked(MY_WRITER_VAR.buf, 1, MY_WRITER_VAR.s, stdout);
    MY_WRITER_VAR.s = 0;
  }
  MY_WRITER_VAR.buf[MY_WRITER_VAR.s++] = a;
}
inline void wt_L(char a){
  my_putchar_unlocked(a);
}
inline void wt_L(const char c[]){
  int i=0;
  for(i=0;c[i]!='\0';i++){
    my_putchar_unlocked(c[i]);
  }
}
int N;
char S[1002];
int a[1000];
int main(){
  int Lj4PdHRW;
  int KL2GvlyY = rd_int();
  for(Lj4PdHRW=(0);Lj4PdHRW<(KL2GvlyY);Lj4PdHRW++){
    int i;
    rd(N);
    rd(S);
    for(i=(0);i<(N);i++){
      if(S[i]=='o'){
        a[i] =1;
      }
      else if(S[i]=='-'){
        a[i] =0;
      }
      else{
        a[i] =-100;
      }
    }
    for(i=(2);i<(N);i++){
      if(a[i-2]+a[i-1]+a[i] >= 2){
        wt_L("O");
        wt_L('\n');
        goto Q5VJL1cS;
      }
    }
    for(i=(3);i<(N);i++){
      if(S[i-3]=='-' && S[i-2]=='o' && S[i-1]=='-' && S[i]=='-'){
        wt_L("O");
        wt_L('\n');
        goto Q5VJL1cS;
      }
    }
    for(i=(3);i<(N);i++){
      if(S[i-3]=='-' && S[i-2]=='-' && S[i-1]=='o' && S[i]=='-'){
        wt_L("O");
        wt_L('\n');
        goto Q5VJL1cS;
      }
    }
    wt_L("X");
    wt_L('\n');
    Q5VJL1cS:;
  }
  return 0;
}
// cLay varsion 20200404-1

// --- original code ---
// int N; char S[1002];
// int a[1000];
// {
//   REP(rd_int()){
//     rd(N,S);
//     rep(i,N) a[i] = if[S[i]=='o', 1, S[i]=='-', 0, -100];
//     rep(i,2,N) if(a[i-2]+a[i-1]+a[i] >= 2) wt("O"), break_continue;
//     rep(i,3,N) if(S[i-3]=='-' && S[i-2]=='o' && S[i-1]=='-' && S[i]=='-') wt("O"), break_continue;
//     rep(i,3,N) if(S[i-3]=='-' && S[i-2]=='-' && S[i-1]=='o' && S[i]=='-') wt("O"), break_continue;
//     wt("X");
//   }
// }