Untitled

#include <iostream>
using namespace std;

void task(const string& ip) {
    int freq[126] = {0};
    string unique;

    for (const auto& each_char : ip) {

        if (freq[each_char] == 0)
            unique.push_back(each_char);
        ++freq[each_char];
    }

    
    for(const auto& each_unique_char : unique){

        char temp = (char)(freq[each_unique_char] + ('A' - 1));
        cout << temp;
    }
}

int main()
{
    string input = "abbbcccddaab";

    task(input);
}