99 identical balls lie on a table. 50 balls are made of copper, and 49 balls are made of zinc. The assistant numbered the balls. Once a spectrometer test is applied to 2 balls, it allows determining whether they are made of the same metal or not. However, the results of the test can be obtained only the next day. What is the minimum number of tests required to determine the material of each ball if all the tests should be performed today?

Let's think step by step and output the final answer within \boxed{}.
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