n = 6 a[] = {1, 1, 5, 2, 5, 5} answer = 1 ( swap a[0] with a[4] or a[5] )

n = 8 a[] = {1, 5, 5, 1, 4, 6, 1, 1} answer = 2 (swap a[0] with a[1] and a[5] with a[6] )

n = 8 a[] = {3, 1, 1, 5, 3, 3, 5, 5} answer = 2 (swap a[0] with a[1] and a[5] with a[6] )

indexing from zero in above examples.