Task: Text Categorization
Input (English): Following the revolution of the Young Turks, Prince Ferdinand of Saxe-Coburn-Gotha proclaimed himself king of this country, which lost South Dobruja in a 1913 treaty. While under Turkish rule, Stefan Stambulov led a rebellion here in 1876, and later, the Congress of Berlin reduced the size of this country by revising the very generous Treaty of San Stefano. Long ruled by the Communist Todor Zhivkov, for 10 points, name this Balkan country, the successor to a medieval empire whose tsars Simeon and Samuel fought the Byzantines to its east.
Output (English): History