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class Solution {
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  String modifiedNumber = "";
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  public String reformatNumber(String number) {
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    modifiedNumber = number.replace(" ", "");
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    modifiedNumber = modifiedNumber.replace("-", "");
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    int l = modifiedNumber.length();
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    if (l <= 3) {
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      return modifiedNumber;
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    } else if (l == 4) {
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      return modifiedNumber.substring(0, 2) + "-" + modifiedNumber.substring(2, 4);
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    } else {
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      modifiedNumber =
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          modifiedNumber.substring(0, 3) + "-" + reformatNumber(modifiedNumber.substring(3, l));
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    }
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    return modifiedNumber;
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  }
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}