import java.util.*;
import java.lang.*;
import java.io.*;

class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		int[] array = {1,2,2,1,1,3,3,1,3};		
		Arrays.sort(array);
		
		int pairs = 0; 
		int times = 1;
		for (int i = 1; i < array.length; i++) {
		    if (array[i] == array[i-1]) {
		        ++times;
		    } else {
		        pairs += times*(times-1) / 2;
		        times = 1;
		    }                   
		}
		pairs += times*(times-1) / 2;
		System.out.println(pairs);         		
	}
}