Question: How many years after the Schengen Treaty being signed did the 2017 Dutch–Turkish diplomatic incident occur? Passage:At the time, the Turkish Minister of Family and Social Policies, Fatma Betül Sayan Kaya, was touring Germany. A visit to the Dutch town of Hengelo, close to the German border, had already been scheduled. On 11 March, the Dutch General Intelligence and Security Service received information that Kaya would try to reach Rotterdam by car. She could freely cross the border because of the Schengen Treaty. A crisis centre was established on the twenty-third floor of the Rotterdam World Port Center to coordinate police actions. Earlier, the Turkish consul in Rotterdam had indicated to the Mayor of Rotterdam, Ahmed Aboutaleb, that there were no plans for such a visit. It now proved impossible to contact the consul, which gave Aboutaleb the conviction that the consul knew of Kaya's attempt. A motorcade was intercepted but the car with the minister managed to drive away. It reached a small yard at the rear of the Turkish consulate. The Dutch police stopped Betül Sayan Kaya's entourage just metres from the Turkish consulate building. About twenty police officers, forming a special forces unit, the Dienst Speciale Interventies, masked and equipped with body armour and automatic weapons, arrested ten members of Kaya's bodyguard, on suspicion of illegally carrying firearms. A German source had indicated they had obtained a German weapons permit. No arms were discovered. Two other men were also arrested, who later proved to be the Deventer Turkish consul and the chargé d'affaires of the Turkish embassy. They in principle enjoyed diplomatic immunity. The twelve arrested men were detained for two hours and their passports were seized. A stand-off ensued for several hours in which the Turkish minister refused to leave the car. Just after midnight, a special heavy tow truck, a lift flatbed, was driven into the yard and prepared to vertically hoist the 3.5 tonne car onto the flatbed, with the minister still in it, to transport her back to Germany. The minister now left the car and demanded entrance to the consulate invoking the Vienna Convention on Diplomatic Relations. The Dutch police had orders to arrest the minister if necessary. Ultimately, she gave in to the police demands to leave the country. At the time, many news sources assumed that she had been declared persona non grata. She was, loudly protesting, taken to another car, a black armoured Mercedes, by masked Dutch police officers who accompanied her to a police station at Nijmegen near the Dutch–German border. Her passport was seized. She was not allowed to leave the station for one and a half hours, while being reunited with the ten bodyguards. She returned to Germany under German escort. Sporadic rioting occurred among the about a thousand pro-Erdoğan protesters who had come to the Turkish consulate. They were met by Dutch riot police, who arrested twelve people for violent assault and not following police instructions. Kaya's passport was returned on 12 March, 18:00, to the Turkish consul. In April 2017, Kaya's lawyer said they would file a complaint against the Dutch government at court claiming that her expulsion from the Netherlands was illegal because she was not given a written statement of the reasons for the expulsion. However, on 2 May the case was dropped when it transpired that Kaya had never been formally declared persona non grata and that from a judicial point of view she had left the Netherlands voluntarily.

Output: b