Given the task definition and input, reply with output. This task involves annotating the answer type to a given question that involve some kind of complex reasoning (including numerical reasoning). Note that the questions require looking at more than one part of the passage to answer. There are 3 possible answer types (i) spans, (ii) numbers and (iii) dates. If the answer can be found in the passage, label it as "span". If the answer is a number, label as "number". Similarly, label "date" if you think the answer to the given question is a date.

Passage: Bulgaria is officially a secular nation and the Constitution guarantees the free exercise of religion but designates Orthodoxy as a "traditional" religion. In the 2001 census, 82.6% Bulgarians declared themselves Orthodox Christians, 12.2% Muslim, 1.2% other Christian denominations, 4% other religions and zero percent atheists. Most citizens of Bulgaria have associations at least nominally with the Bulgarian Orthodox Church. Founded in 870AD under the Patriarchate of Constantinople , the Bulgarian Orthodox Church had autocephalous status since 927 AD. The Church became subordinate within the Patriarchate of Constantinople, twice during the periods of Byzantine and Ottoman domination. It was re-established first in 1870 in the form of the Bulgarian Exarchate, and then in the 1950s as the Bulgarian Patriarchate.
Question: What is this paragraph mainly about?
span