Merkkijono

#include <bits/stdc++.h>
using namespace std;

int main() {
	int j;
	string::size_type i;
	string a;
	cin >> a;
	
	i = 0;
	j = 1;
	while (i < a.length()) {
		while (a[i] == a[i+j]) {
			j++;
		}
		if (j > 1) {
			a.erase(i, j);
			j = 1;
			if (i > 0) {
				i -= 2;
			} else {
				i--;
			}
		}
		i++;
	}
	cout << a;

	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