From Sensei

#include <iostream>
using namespace std;
bool isdg(string s)
{
    for (int i = 0; i < s.length(); i++)
    {
        if (!isdigit(s[i]))
            return false;
    }
    return true;
}
int main()
{
    int tests;
    cin >> tests;
    string input;
    while (tests--)
    {
        cin >> input;
        int str_len = input.length();
        int r_pos = input.find('R');
        int c_pos = input.find('C');
        if (c_pos != -1 && r_pos != -1 && c_pos > 1 && isdg(input.substr(1, c_pos - 1)))
        {

            int row_num = stoi(input.substr(1, c_pos - 1));
            int col_num = stoi(input.substr(c_pos + 1));
            string result = "";
            while (col_num > 0)
            {
                int index = (col_num - 1) % 26;
                result = (char)(index + 'A') + result;
                col_num = (col_num - 1) / 26;
            }
            cout << result << row_num << endl;
        }
        else
        {
            int row_num_index = 0;
            for (int i = 0; i < str_len; i++)
            {
                if (isdigit(input[i]))
                {
                    row_num_index = i;
                    break;
                }
            }
            string col_letters = input.substr(0, row_num_index);
            int result = 0;
            for (int i = 0; i < col_letters.length(); i++)
            {
                result *= 26;
                result += col_letters[i] - 'A' + 1;
            }
            row_num_index = stoi(input.substr(row_num_index, str_len - row_num_index));
            cout << "R" << row_num_index << "C" << result << endl;
        }
    }
}