function el(n){
  var a = 0;
  var b = 1;
  var c;
  var f = [];
  var s = [];
  for(var i = 0;i <= n;i++){
    c = a + b;
    a = b;
    b = c;
    f.push(a);
    if(f.includes(i)){
        s.push('O');
       }else if(i > 0){
         s.push('o');
       }
  }
  s = s.join('');
  return s;
};
el(8);