Task: Question Generation
Input (English): Barcelona won the treble in the 2014–2015 season, winning La Liga, Copa del Rey and UEFA Champions League titles, and became the first European team to have won the treble twice. On 17 May, the club clinched their 23rd La Liga title after defeating Atlético Madrid. This was Barcelona's seventh La Liga title in the last ten years. On 30 May, the club defeated Athletic Bilbao in the Copa del Rey final at Camp Nou. On 6 June, Barcelona won the UEFA Champions League final with a 3–1 win against Juventus, which completed the treble, the club's second in 6 years. Barcelona's attacking trio of Messi, Suárez and Neymar, dubbed MSN, scored 122 goals in all competitions, the most in a season for an attacking trio in Spanish football history.
Output (English): What competition did Barcelona win on May 17 of the 2014-15 season?