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Ural Regional School Programming Contest 2011

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F. Rubinchik's Cube

Time limit: 0.5 second
Memory limit: 64 MB
Problem illustration
Striving to develop their intellectual skills, the players of the Psych Up team decided to learn how to solving a Rubik's cube. After a week, they gave up the attempt in despair. Instead, they decided to solve a simpler 2 × 2 × 2 Rubik's cube but also failed. Then the team leader Misha invented a cube that was even simpler.
The new cube consists of four layers of size 4 × 4. Each layer is made of glass and is absolutely transparent. The upper face of each layer is divided into 16 equal squares. Four of them are painted red, yellow, blue, or green. There is a hole at the center of each layer. A solid rod is put through the holes so that the layers can be turned independently of each other.
The layers look as follows.
Problem illustration
The cube is solved if it is in one of the following states (top view).
Problem illustration
It was hard to solve the cube, but the Psych Up team did it. Your task will be even harder! You must solve the cube from a given state in a minimum number of turns. One turn is a turn of one layer by 90 degrees in any direction.


You are given four lines, each containing four integers, which describe the current state of the cube (top view). The numbers are in the range from 1 to 4; they correspond to the colors of the cube's squares. Different numbers denote different colors.


Output the minimum number of turns needed for solving the cube.


2 1 2 3
1 1 2 2
4 4 3 3
1 4 3 4
Problem Author: Denis Mukhametianov
Problem Source: Ural Regional School Programming Contest 2011
To submit the solution for this problem go to the Problem set: 1878. Rubinchik's Cube