RT，实在想不到哪里会越界。

#include <bits/stdc++.h>

using namespace std;

int n, tot, ans;
string s, st;

int main () {
	
	// freopen ("game.in", "r", stdin);
	// freopen ("game.out", "w", stdout);
	
	cin >> n >> s;
	
	int slen = s.size ();
	for (int i = 0; i < slen; ++ i) {
		
		tot = 0;
		
		for (int j = i; j < slen; ++ j) {
			
			if (st[tot] != s[j] || tot == 0) 
				st[++ tot] = s[j];
			
			else {
			
				if (st[tot] == s[j] && tot != 0)
					tot --;
				if (tot == 0)
					ans ++;	
			}
		}
	}
	
	cout << ans;
	
	return 0;
}