1
/**
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 * @param {number} k
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 * @return {number}
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 */
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var smallestRepunitDivByK = function (k) {
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  if (1 > k > 1e6) return -1;
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  let val = 0;
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  for (let i = 1; i < 1e6; i++) {
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    val = (val * 10 + 1) % k;
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    if (val === 0) return i;
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  }
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  return -1;
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};