小图灵测得……

#include <bits/stdc++.h>

using namespace std;

const int kMaxN = 2e6 + 5;

long long n, top, ans;
char sta[kMaxN];
string s;

int main() {
	freopen("game.in", "r", stdin);
	freopen("game.out", "w", stdout);
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    cin >> n >> s;
    s = " " + s;
    for (int i = 1; i <= n; i++) {
        top = 0;
        if (clock() >= 980) {
        	return cout << ans, 0;
		} 
        for (int j = i; j <= n; j++) {
            sta[++top] = s[j];
            if (top >= 2 && sta[top] == sta[top - 1]) {
                top -= 2;
            }
            ans += (top == 0);
       }
    }
    cout << ans;
	return 0;
} 

期望50