Merkkijono

#include <iostream>
#include <string>
#include <cctype>
#include <algorithm>

int main(int argc, char* argv[])
{
	std::string str;
	std::cin >> str;
	int loop = 1;
	for(unsigned int i = 0; i < str.length(); i++)
		if(/*!isupper(str[i]) ||*/ !isalpha(str[i]))
		{
			str.erase(i, 1);
			i--;
		}

	while(loop)
	{
		loop = 0;
		for(unsigned int i = 0; i < str.length(); i++)
		{
			char current = toupper(str[i]);

			int j;
			for(j = 0; toupper(str[i + j]) == current; j++);
			if(j > 1)
			{
				str.erase(i, j);
				loop = 1;
				i=0;
			}
		}
	}

	for(unsigned int i = 0; i < str.length(); i++)
		std::cout << (char)toupper(str[i]);
	std::cout << std::endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED