3986번-좋은 단어

#include<iostream>
#include<stack>
#include<string>
using namespace std;

int main() {
	int n;
	int ans = 0;
	cin >> n;
	while (n--) {
		string a;
		cin >> a;
		stack<char> s;
		for (auto c : a) {
			if (!s.empty() && s.top() == c)s.pop();
			else s.push(c);
		}
		if (s.empty())ans++;
	}
	cout << ans << "\n";
}