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class Solution {
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 public:
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  string thousandSeparator(int n) {
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    string s = "";
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    int a = 0;
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    if (n == 0) return "0";
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    while (n > 0) {
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      s += char(n % 10 + 48);
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      a++;
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      n /= 10;
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      if (a == 3 && n != 0) {
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        a = 0;
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        s += ".";
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      }
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    }
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    reverse(s.begin(), s.end());
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    return s;
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  }
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};