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# Gena Playing Hanoi

# Gena Playing Hanoi

The Tower of Hanoi is a famous game consisting of rods and a number of discs of incrementally different diameters. The puzzle starts with the discs neatly stacked on one rod, ordered by ascending size with the smallest disc at the top. The game's objective is to move the entire stack to another rod, obeying the following rules:

- Only one disk can be moved at a time.
- In one move, remove the topmost disk from one rod and move it to another rod.
- No disk may be placed on top of a
*smaller*disk.

Gena has a modified version of the Tower of Hanoi. This game of *Hanoi* has rods and disks ordered by ascending size. Gena has already made a few moves following the rules above. Given the state of Gena's *Hanoi*, determine the minimum number of moves needed to restore the tower to its original state with all disks on rod .

**Note:** Gena's rods are numbered from to . The radius of a disk is its index in the input array, so disk is the smallest disk with a radius of , and disk is the largest with a radius of .

**Example**

In this case, the disks are arranged from large to small across the four rods. The largest disk, disk , is already on rod , so move disks and to rod , in that order. It takes moves to reset the game.

The largest disk, disk with radius , is already on rod . Disk is on rod and must be below disk . Move disk to rod , disk to rod and disk to rod . Now move disk to rod . It takes moves to reset the game.

**Function Description**

Complete the *hanoi* function below.

*hanoi* has the following parameters:

*int posts[n]:*is the location of the disk with radius

**Returns**

*int:*the minimum moves to reset the game to its initial state

**Input Format**

The first line contains a single integer, , the number of disks.

The second line contains space-separated integers, where the integer is the index of the rod where the disk with diameter is located.

**Constraints**

**Sample Input**

STDIN Function ----- -------- 3 size of posts[] n = 3 1 4 1 posts = [1, 4, 1]

**Sample Output**

```
3
```

**Explanation**

moves are enough to build the tower. Here is one possible solution: