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How many teams played in the tournament?

Source: Mexican Mathematical Olympiad 2004 OMM P4

July 31, 2018
combinatoricsTournament

Problem Statement

At the end of a soccer tournament in which any pair of teams played between them exactly once, and in which there were not draws, it was observed that for any three teams A,BA, B and C, if AA defeated BB and BB defeated CC, then AA defeated CC. Any team calculated the difference (positive) between the number of games that it won and the number of games it lost. The sum of all these differences was 50005000. How many teams played in the tournament? Find all possible answers.