Merkkijono

#include <iostream>
#include <string>
 
using namespace std;
 
int main() {
	std::string d;
	int i = 0;
	int r = 0;
 
	cin >> d;
	while (d[i]) {
		if (d[i] == d[i + 1]) {
			r++;
		} else {
			if (r) { 
				d.erase(i-r, r+1); 
				i -= r; 
				if (i) i--;
				r = 0;
				continue; 
			}
		}
		i++;
	}
	
	cout << d << '\n';
}

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