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class Solution {
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  public int shortestSequence(int[] rolls, int k) {
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    int len = 0;
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    Set<Integer> set = new HashSet<>();
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    for (int i : rolls) {
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      set.add(i);
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      if (set.size() == k) {
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        set = new HashSet<>();
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        len++;
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      }
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    }
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    return len + 1;
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  }
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}