桁,bit

int main() {
	string N; cin >> N;
	int n = N.size();
	int K; cin >> K;
	ll dp[110][2][4];
	REP(i, 110) {
		REP(j, 2) {
			REP(k, 4) {
				dp[i][j][k] = 0;
			}
		}
	}
	dp[0][0][0] = 1;
	for (int i = 0; i < n; ++i) {
		for (int j = 0; j < 2; ++j) {
			for (int k = 0; k <= K; ++k) {
				int x;
				x = j ? 9 : N[i] - '0';
				for (int d = 0; d <= x; ++d) {
					if (d != 0) {
						if (k < K) {
							dp[i + 1][j || (d < x)][k + 1] += dp[i][j][k];
						}
					}
					else {
						dp[i + 1][j||(d<x)][k] += dp[i][j][k];
					}
				}
			}
		}
	}
	cout << dp[n][0][K] + dp[n][1][K] << endl;
	return 0;
}