a-b=4 inseamna ca a=9,8,7,6,5,4 si b=5,4,3,2,1,0
deci aven numerele 950.951.952.953.954.955.956.957.958.959
840.841.842.843.844.845.846.847.848.849
730.731.732.733.734.735.736.737.738.739
620.621.623.624.625.626.627.628.629
510.511.512.513.514.515.516.517.518.519
400.401.402.403.404.405.406.407.408.409