Untitled

#include <iostream>
#include <string>

int main()
{
    std::string str = "A%3,B:4,C:2,D%3,E:5";

    std::string keys = ""; 
    // String to store keys
    for (int i = 0; i < str.size(); i++)
    {
        if (str[i] >= 'A' && str[i] <= 'Z')
        { 
            char key = str[i];
            if (keys.find(key) != std::string::npos)
                continue;
            int value;
            if (str[i + 1] == ':' || str[i + 1] == '%')
            {                          // Check  ':' or '%'
                value = str[i + 2] - '0'; // Convert char digit to int
            }
            if (value <= 3)
            {
                keys += key; // Append the key 
                std::cout << key << std::endl;
            }
        }
    }

    return 0;
}