题目描述
The goal of the 15 puzzle problem is to complete pieces on $4 \times 4$ cells where one of the cells is empty space.
In this problem, the space is represented by 0 and pieces are represented by integers from 1 to 15 as shown below.
1 2 3 4
6 7 8 0
5 10 11 12
9 13 14 15
You can move a piece toward the empty space at one step. Your goal is to make the pieces the following configuration in the shortest move (fewest steps).
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 0
Write a program which reads an initial state of the puzzle and prints the fewest steps to solve the puzzle.
Constraints
- The given puzzle is solvable in at most 45 steps.
Input
The $4 \times 4$ integers denoting the pieces or space are given.
Output
Print the fewest steps in a line.
Example
Input
1 2 3 4
6 7 8 0
5 10 11 12
9 13 14 15
Output
8
输入格式
见题面
输出格式
见题面