Minimum Amount of Time to Fill Cups LeetCode solution in JavaScript

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var fillCups = function (amount) {
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  var count = 0;
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  var a = amount;
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  while (eval(a.join("+")) > 0) {
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    var max = Math.max(...a);
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    a.splice(a.indexOf(max), 1);
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    var max2 = Math.max(...a);
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    a.splice(a.indexOf(max2), 1);
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    count++;
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    if (max == 0) a.push(0);
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    else a.push(max - 1);
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    if (max2 == 0) a.push(0);
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    else a.push(max2 - 1);
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  }
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  return count;
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};