class Solution {
public:
    /**
     * 进制转换
     * @param M int整型 给定整数
     * @param N int整型 转换到的进制
     * @return string字符串
     */
    string solve(int M, int N) {
        // write code here
        string res = "";
        vector<char> rec = {'0', '1', '2', '3', '4', '5', '6', '7', 
                           '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
        int index = 0, flag=0;
        if(M < 0){
            M = -M;
            flag = 1;
        }
        while(M > 0){
            index = M % N;
            M = M / N;
            res.push_back(rec[index]);
        }
        if(flag){
            res.push_back('-');
        }
        reverse(res.begin(), res.end());
        return res;
    }
};