Magic is in the air

There's a new magician in dino-town. He can make X or more consecutive coloured playing cubes magically disappear with his wand. He has a large number of coloured playing cubes and he wishes to find the smallest number of cubes he should insert into the sequence so that he can make all of them vanish, keeping in mind that he can insert the cubes anywhere in the sequence, at the beginning, in betwe