Task: Question Generation
Input (English): Passage: Following World War II, Britain retained control of both British Somaliland and Italian Somaliland as protectorates. In 1950, as a result of the Paris Peace Treaties, the United Nations granted Italy trusteeship of Italian Somaliland, but only under close supervision and on the condition—first proposed by the Somali Youth League  and other nascent Somali political organizations, such as Hizbia Digil Mirifle Somali  and the Somali National League —that Somalia achieve independence within ten years. British Somaliland remained a protectorate of Britain until 1960. In 1948, under pressure from their World War II allies and to the dismay of the Somalis, the British returned the Haud  and the Ogaden to Ethiopia, based on a treaty they signed in 1897 in which the British, French and Italians agreed upon the territorial boundaries of Ethiopia with the Ethiopian Emperor Menelik in exchange for his help against raids by hostile clans. Britain included the provision that the Somali residents would retain their autonomy, but Ethiopia immediately claimed sovereignty over the area. This prompted an unsuccessful bid by Britain in 1956 to buy back the Somali lands it had turned over. Britain also granted administration of the almost exclusively Somali-inhabited Northern Frontier District  to Kenyan nationalists despite an informal plebiscite demonstrating the overwhelming desire of the region's population to join the newly formed Somali Republic.
Output (English): How many years after the British returned the Haud an the Ogaden to Ethiopia did Brtain unsuccessfully bid to buy back Somali lands it had turned over?