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He has participated in hiking adventures on Mount Olympus in Greece , Rila in Bulgaria , Feldberg in Germany , Materhorn in Switzerland , Mont Blanc in France and in numerous Montenegrin mountains as well .
 Greece, Germany, Switzerland, France
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Greece, Germany, Switzerland, France