Who built Petra?
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Petra is an example of a city.
The city of Petra is an example of a city .
Who built Petra?</s>Petra is an example of a [unused1]city                [unused2] .
Who built Petra?</s>Petra is an example of a city.
Who built Petra?</s>The [unused1]city                [unused2] of Petra is an example of a
Who built Petra?</s>The city of Petra is an example of a city .
Who built Petra?</s>[unused1]city[unused2],0,[unused1]city[unused2],[unused1]city[unused2],0,Petra,Petra,instance of,[unused1]city[unused2],Petra,0,Petra
Who built Petra?</s>city,0,city,city,0,Petra,Petra,instance of,city,Petra,0,Petra