Calculate Money in Leetcode Bank LeetCode solution in Java

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class Solution {
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  public int totalMoney(int n) {
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    int m = n / 7; // (no.of full weeks)
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    // first week 1 2 3 4 5 6 7 (sum is 28 i.e. 7*(i+3) if i=1)
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    // second week 2 3 4 5 6 7 8 (sum is 35 i.e. 7*(i+3) if i=2)
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    // .... so on
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    int res = 0; // for result
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    // calculating full weeks
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    for (int i = 1; i <= m; i++) {
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      res += 7 * (i + 3);
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    }
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    // calculating left days
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    for (int i = 7 * m; i < n; i++) {
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      res += ++m;
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    }
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    return res;
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  }
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}