Customers are standing in a queue to buy from you, and order one at a time (in the order specified by `bills`).

Each customer will only buy one lemonade and pay with either a `\$5``\$10`, or `\$20` bill.  You must provide the correct change to each customer, so that the net transaction is that the customer pays \$5.

Note that you don't have any change in hand at first.

Return `true` if and only if you can provide every customer with correct change.

Example 1:

```Input: [5,5,5,10,20]
Output: true
Explanation:
From the first 3 customers, we collect three \$5 bills in order.
From the fourth customer, we collect a \$10 bill and give back a \$5.
From the fifth customer, we give a \$10 bill and a \$5 bill.
Since all customers got correct change, we output true.```

Example 2:

``````Input: [5,5,10]
Output: true
``````

Example 3:

``````Input: [10,10]
Output: false
``````

Example 4:

``````Input: [5,5,10,10,20]
Output: false
Explanation:
From the first two customers in order, we collect two \$5 bills.
For the next two customers in order, we collect a \$10 bill and give back a \$5 bill.
For the last customer, we can't give change of \$15 back because we only have two \$10 bills.
``````

Note:

• `0 <= bills.length <= 10000`
• `bills[i]` will be either `5``10`, or `20`.

```class Solution {
public:
int five = 0, ten = 0;
for (int bill : bills) {
if (bill == 5) ++five;
else if (bill == 10) { --five; ++ten; }
else if (ten > 0) { --ten; --five; }
else five -= 3;
if (five < 0) return false;
}
return true;
}
};```