Merkkijono

#include <iostream>
#include <string>


int main(){
    
    //Read the string and create the main iterator
    std::string str;
    std::cin >> str;
    auto it = str.begin();

    //Main loop
    do{
        //First step
        char lastChar = *it;
        it++;

        while(it != str.end()){
            
            //If this char is the same as the last one
            if(lastChar == *it){

                auto sameBegin = it -1;
                auto sameEnd = it;

                //Increase end until either the string ends or the last is no longer the same char
                while(sameEnd != str.end() && *sameEnd == lastChar){
                    sameEnd++;
                }

                //Erase the range and set the iterator to the beginning(signifies that the string has changed)
                str.erase(sameBegin, sameEnd);
                it = str.begin();
                break;
            }
            //If not, move forward
            else{
                lastChar = *it;
                it++;
            }
            
        }
    
        //Run main loop until either the string hasn't changed or it's only the length of one on zero
    } while(it == str.begin() && str.length() > 1);
    
    std::cout << str << "\n";

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED