Problem Statement  
Christmas is just around the corner, and Alice just decorated her Christmas tree.
There are N stars and N1 ribbons on the tree.
Each ribbon connects two of the stars in such a way that all stars and ribbons hold together.
(In other words, the stars and ribbons are the vertices and edges of a tree.)
The stars are numbered 1 through N.
Additionally, each star has some color.
You are given the colors of stars as a int[] col with N elements.
For each i, col[i] is the color of star i+1.
(Different integers represent different colors.)
You are also given a description of the ribbons: two int[]s x and y with N1 elements each.
For each i, there is a ribbon that connects the stars with numbers x[i] and y[i].
According to Alice, a ribbon that connects two stars with different colors is beautiful, while a ribbon that connects two samecolored stars is not.
Compute and return the number of beautiful ribbons in Alice's tree.
  Definition   Class:  ChristmasTreeDecorationDiv2  Method:  solve  Parameters:  int[], int[], int[]  Returns:  int  Method signature:  int solve(int[] col, int[] x, int[] y)  (be sure your method is public) 
    Constraints    N will be between 2 and 50, inclusive.    The number of elements in col will be exactly N.    The number of elements in x will be exactly N  1.    The number of elements in y will be the same as the number of elements in x.    All elements of x and y will be between 1 and N, inclusive.    For each i, the numbers x[i] and y[i] will be different.    The graph formed by the N1 ribbons will be connected.   Examples  0)     Returns: 2  There are two beautiful ribbons: the one that connects stars 1 and 2, and the one that connects stars 2 and 3.
The other ribbon is not beautiful because stars 3 and 4 have the same color. 

 1)     2)     3)     4)    
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