query: SELECT DISTINCT  ?item ?country ?age
  WHERE { 
    ?country wdt:P31 wd:Q3624078 ; wdt:P1313 ?office . 
    ?office wdt:P1308 ?item .
    ?item wdt:P569 ?birthdate .
    FILTER (!isBLANK(?birthdate))
    BIND(ROUND((NOW() - ?birthdate)/365.2425) AS ?age)
  }
  ORDER BY DESC(?birthdate)
  LIMIT 20