class Solution {
public:
    string convertToBase7(int num) {

        if(num == 0 ) return "0";
        if( num <  0 ) return "-" + convertToBase7(-num);

        string res = "";

        while( num >  0 )
        {
            res += to_string(num%7);
            num = num/7;
        }

        reverse(res.begin(), res.end());
        return res;
    }
};