Largest number formed by N digit and digit sum equals to S

N , sum=S 0 < N ⇐10^5 0 < S ⇐ 10

Ex: N = 4 S = 20

n =2 s =15

// check if sum is possible N = 6 S = 34 9+9+9+9+9+9= 9*6 = 54 sum must be always ⇐ 54 9+9+9+0+0+0 9+9+9+1+1+1 9+9+9+2+1+1 9+9+9+5+1+1