math box p math ''p'' case every time ''t'' trade operators deal future past example math diamond p math '''f'''''p'' math box p math '''g'''''p'' math diamond p math ''p'' '''f'''''p'' math box p math ''p'' '''g'''''p'' operators '''f''' '''g''' may seem initially foreign create normal modal systems note '''f'''''p'' '''g''' ''p'' combine operators form complex statements example '''p'''''p'' '''p'''''p'' says effectively ''everything
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