Help me which case I am missing


#1
class Solution:
# @param A : integer
# @param B : integer
# @return an integer
def solve(self, N, S):
    dp = [[ 0 for i in  range(S+1)] for j  in range(N+1)]
    i=2
    j=1
    while(j<=S and j<=9):
        dp[1][j]=1
        j+=1
    while(i<=N):
        j=1
        while(j<=S):
            dp[i][j]=(dp[i-1][j]+dp[i][j-1])%1000000007
            if j>9:
                dp[i][j]-=dp[i][j-10]
            dp[i][j]=dp[i][j]%1000000007
            j+=1
        i+=1
    return dp[N][S]%1000000007