class Solution {
public:
    int totalMoney(int n) {
        auto sum = [](int a0, int n, int d) -> int {return a0*n+(n*(n-1)*d)/2; };
        int week = n / 7;
        int money = 0;
        money += sum(28, week, 7);
        int day = n % 7;
        money += sum(1 + week, day, 1);
        return money;
    }
};

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