C # program to count the number of numbers formed by digits a and b exactly of a length N such that the sum of the digits of the number thus formed is of digits a and b .
using System ; class GFG { static int mod = ( int ) ( 1e9 + 7 ) ; static int N = 1000005 ; static int [ ] fact = new int [ N ] ; static int [ ] invfact = new int [ N ] ;