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- 10

## Learning Opportunities

This puzzle can be solved using the following concepts. Practice using these concepts and improve your skills.

## Statement

## Goal

Part one : https://www.codingame.com/training/easy/the-prime-twins---part-one**Context :**

五 and 七, two brilliant young students in middle school, have just finished creating their own secret language during the holidays. Proud of their creation, they speak confidently, convinced that no one will ever be able to decipher their messages.

**Encryption principles :**

**•**

`i`denotes the integer between a pair of prime twins. For example, between 5 and 7,

`i`= 6.

**•**

`key`represents the secret key agreed upon by 五 and 七.

**Transformation rules :**

A is transformed into

`key`+

`key`. For subsequent letters like B and beyond,

`key`is added to the integer located between the closest pair of prime twins that is strictly greater than the previous value. For example, if the previous value was

`i`, the search for the next pair of twins starts from

`i`+ 1.

**Example :**

If

`key`= 3, A = 3 + 3 = 6. For B, the search for prime twins starts strictly above 6, and the closest twins will be 11 and 13, so

`i`= 12 and B = 3 + 12 = 15. For C, starting strictly above 15, the next twins will be 17 and 19, so

`i`= 18 and C = 3 + 18 = 21.

**Input format :**

For an

`operation`,

`message`contains only upper case letters and spaces.

For a

`operation`,

`message`contains only upper case hexadecimal values and the upper case letter

**Output format :**

The resulting integers are then converted to hexadecimal in upper case, separated by

**ABC**is transformed into

**6, 15, 21**, which is then converted to

**6**G FG 15.

**Error case :**

If

`message`does not comply with its respective input format, you must return

**Goal :**

Develop code to decode or encode the secret language of 五 and 七.

Input

**Line 1**: string

`operation`

**Line 2**: integer

`key`Secret key agreed upon by 五 and 七

**Line 3**: string

`message`

Output

encoded or decoded upper case letter message / "ERROR !! "

Constraints

2 <=

`key`<= 5*10⁶`message`contains only upper case letters and spacesExample

Input

ENCODE 3 ABC

Output

6GFG15

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