A Survey of 100 College Students Who Frequent the Reading

A survey of 100 college students who frequent the reading lounge of a university revealed the following results:
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47 read Time.
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36 read Newsweek.
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31 read U.S. News & World Report.
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19 read Time and Newsweek.
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16 read Time and U.S. News & World Report.
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12 read Newsweek and U.S. News & World Report.
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6 read all three magazines.
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How many of the students surveyed read none of these magazines?
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__________ students