Merkkijono

#include <iostream>
#include <string>
#include <vector>

template <typename InputIt>
std::string remove(InputIt str_begin, InputIt begin, InputIt end) {
    std::string str;
    str.reserve(std::distance(str_begin, begin));
    str.assign(str_begin, begin);

    auto it = begin;
    while (*begin == *it) {
        ++begin;
    }
    str.append(begin, end);

    return str;
}

int main() {
    std::string str;
    std::cin >> str;
    for (auto it = str.begin() + 1; it != str.end(); ++it) {
        if (*it == *(it - 1)) {
            str = remove(str.begin(), it - 1, str.end());
            it = str.begin();
        }
    }
    std::cout << str << '\n';
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: RUNTIME ERROR

Test 3

Verdict: RUNTIME ERROR

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