1
var powerfulIntegers = function (x, y, bound) {
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  let ans = new Set();
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  for (let xi = 1; xi < bound; xi *= x) {
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    for (let yj = 1; xi + yj <= bound; yj *= y) {
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      ans.add(xi + yj);
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      if (y === 1) break;
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    }
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    if (x === 1) break;
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  }
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  return Array.from(ans);
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};