# 1622. Fancy Sequence

<https://leetcode.com/problems/fancy-sequence>

## Description

Write an API that generates fancy sequences using the `append`, `addAll`, and `multAll` operations.

Implement the `Fancy` class:

* `Fancy()` Initializes the object with an empty sequence.
* `void append(val)` Appends an integer `val` to the end of the sequence.
* `void addAll(inc)` Increments all existing values in the sequence by an integer `inc`.
* `void multAll(m)` Multiplies all existing values in the sequence by an integer `m`.
* `int getIndex(idx)` Gets the current value at index `idx` (0-indexed) of the sequence **modulo** `109 + 7`. If the index is greater or equal than the length of the sequence, return `-1`.

**Example 1:**

```
**Input**
["Fancy", "append", "addAll", "append", "multAll", "getIndex", "addAll", "append", "multAll", "getIndex", "getIndex", "getIndex"]
[[], [2], [3], [7], [2], [0], [3], [10], [2], [0], [1], [2]]
**Output**
[null, null, null, null, null, 10, null, null, null, 26, 34, 20]
**Explanation**
Fancy fancy = new Fancy();
fancy.append(2);   // fancy sequence: [2]
fancy.addAll(3);   // fancy sequence: [2+3] -> [5]
fancy.append(7);   // fancy sequence: [5, 7]
fancy.multAll(2);  // fancy sequence: [5*2, 7*2] -> [10, 14]
fancy.getIndex(0); // return 10
fancy.addAll(3);   // fancy sequence: [10+3, 14+3] -> [13, 17]
fancy.append(10);  // fancy sequence: [13, 17, 10]
fancy.multAll(2);  // fancy sequence: [13*2, 17*2, 10*2] -> [26, 34, 20]
fancy.getIndex(0); // return 26
fancy.getIndex(1); // return 34
fancy.getIndex(2); // return 20
```

**Constraints:**

* `1 <= val, inc, m <= 100`
* `0 <= idx <= 105`
* At most `105` calls total will be made to `append`, `addAll`, `multAll`, and `getIndex`.

## ac

```java
```