Question: when did Chiang Kai-shek work as the president of the executive Yuan?
Paraphrase: Chiang Kai-shek was the president of the executive Yuan at what time?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q16574 p:P39 ?s . ?s ps:P39 wd:Q702650 . ?s pq:P582 ?value}