/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		int[] a = {3,5,6,3,3,5};
 
		Integer[] indices = new Integer[a.length];
        for (int i = 0; i < a.length; ++i) indices[i] = i;
 
        Arrays.sort(indices, (i, j) -> Integer.compare(a[i], a[j]));
 
        int count = 0;
		int i = 0;
		while (i < indices.length) {
		  int start = i;
		  while (++i < indices.length && a[indices[i]] == a[indices[start]]);
 
		  int thisCount = i - start;
		  count += thisCount * (thisCount - 1) / 2;
		}
		System.out.println(count);
	}
}

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