## Description

https://leetcode.com/problems/calculate-money-in-leetcode-bank/

Hercy wants to save money for his first car. He puts money in the Leetcode bank **every day**.

He starts by putting in `$1`

on Monday, the first day. Every day from Tuesday to Sunday, he will put in `$1`

more than the day before. On every subsequent Monday, he will put in `$1`

more than the **previous Monday**.

Given `n`

, return *the total amount of money he will have in the Leetcode bank at the end of the *`n`

^{th}* day.*

**Example 1:**

Input:n = 4Output:10Explanation:After the 4^{th}day, the total is 1 + 2 + 3 + 4 = 10.

**Example 2:**

Input:n = 10Output:37Explanation:After the 10^{th}day, the total is (1 + 2 + 3 + 4 + 5 + 6 + 7) + (2 + 3 + 4) = 37. Notice that on the 2^{nd}Monday, Hercy only puts in $2.

**Example 3:**

Input:n = 20Output:96Explanation:After the 20^{th}day, the total is (1 + 2 + 3 + 4 + 5 + 6 + 7) + (2 + 3 + 4 + 5 + 6 + 7 + 8) + (3 + 4 + 5 + 6 + 7 + 8) = 96.

**Constraints:**

`1 <= n <= 1000`

## Explanation

For every 7 numbers, we can increase the start. And we add the number difference between the start and number to the total sum.

## Python Solution

```
class Solution:
def totalMoney(self, n: int) -> int:
total = 0
start = 0
for i in range(1, n + 1):
diff = 7 if i % 7 == 0 else i % 7
total += (start + diff)
if i % 7 == 0:
start = start + 1
return total
```

- Time Complexity: O(N).
- Space Complexity: O(1).