解：

不会请看

#include<bits/stdc++.h>
using namespace std;
int main() {
	int N;
	cin >> N;
	vector<int> dp(N + 1, INT_MAX);
	dp[0] = 0;
	vector<int> six_powers;
	for (int k = 0; ; ++k) {
		int power = pow(6, k);
		if (power > N) break;
		six_powers.push_back(power); 
    }
	vector<int> nine_powers;
	for (int m = 0; ; ++m) {
		int power = pow(9, m);
		if (power > N) break;
		nine_powers.push_back(power); 
    }
	for (int i = 1; i <= N; ++i) {
		dp[i] = dp[i - 1] + 1;
		for (int power : six_powers) {
			if (i - power >= 0) {
				dp[i] = min(dp[i], dp[i - power] + 1); 
            } 
        }
		for (int power : nine_powers) {
			if (i - power >= 0) {
				dp[i] = min(dp[i], dp[i - power] + 1); 
            } 
        }
    }
	cout << dp[N] << endl;
	return 0;
}