FASTEST Solution

include

using namespace std;

char str[101]; int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);

cin >> str;

int top = 0, index = 0;
while(str[++index] != '\0') {
    if(top < 0 || str[index] != str[top]) str[++top] = str[index];
    else --top; 
}

if(top < 0) { cout << "Empty String" << endl; return 0; }
str[top + 1] = '\0';
cout << str << endl; 
return 0; 

}