MOSCOW, July 24 (Reuters) - Russian Olympic chief Alexander Zhukov said on Sunday a ruling by the International Olympic Committee (IOC) not to impose a blanket ban on Russia was on of the hardest decisions in the history of the Olympic movement. Zhukov said the decision by the IOC's ruling 15-member executive board was taken unanimously. The Rio Olympics begin on Aug. 5. (Reporting by Alexander Winning; writing by Jack Stubbs; editing by Mark Heinrich) More...