import java.util.Arrays;
import java.util.function.IntFunction;
 
class EqualPairCounter {
    int numberOfEqualPairsQuadratic(int[] arr) {
        int res = 0;
        for (int i = 1; i < arr.length; i++) {
            for (int j = i + 1; j < arr.length; j++) {
                if (i != j && arr[i] == arr[j]) {
                    res++;
                }
            }
        }
        return res;
    }
 
    public static void main(String[] args) {
        int[] arr = new int[] {2,3,5,7,3,9,6,5,6,6,2,4,1,6,3};
        int pairCount = new EqualPairCounter().numberOfEqualPairsQuadratic(arr);
        System.out.printf("Res: %s", pairCount); // => 10
    }
}