/*****************************************
Note：
******************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <unordered_map>
#include <algorithm>
using namespace std;
const int N = 1e6 + 10;
const int INF = 0x3f3f3f3f;

using namespace std;
typedef long long ll;

const int maxn = 3 * 1e5 + 5;

char str[maxn];
unordered_map<ll, int> um;
int main() {
    int n;
    scanf("%d%s", &n, str + 1);

    ll s = 0, ans = 0, a = 0;
    um[0] = 1;

    for(int i = 1; i <= n; i++) {
        if(islower(str[i])) 
        {
            a = str[i] - 'a';
        } 
        else 
        {
            a = str[i] - 'A' + 26;
        }
        s ^=   1LL << a;
        for(int j = 0; j < 52; j++) 
        {
            if(um.count(s ^ (1LL << j))) 
            {
                ans += um[s ^ (1LL << j)];
            }
        }
        if(um.count(s)) 
        {
            ans += um[s];
        }
        um[s]++;
    }
    printf("%lld\n", ans);
    return 0;
}