#include<bits/stdc++.h>

using namespace std;


typedef long long ll;
typedef long double ld;

#define endl "\n"
#define all(a) a.begin(), a.end()
#define pb push_back
#define eb emplace_back
// #define int long long



// Don't Start typing till you complete the idea.


// Check these things for WA and before submitting
// 1. Did you clear all the global arrays
// 2. Did you checked your <= >= < > 
// 3. Did you take the input properly. Did you use break or return while taking input?
// 4. Did you divide by 0.
// 5. Check array , vector , etc size
// 6. in the while loop did you miss something that would cause infinite loop?
// 7. Did you save your dp?
// 8. Are you trying to use something after deleting it?
// 9. Did you read the problem statement wrong?
// 10. Did you check the constrains of the problem properly
// 11. Did you checked for smaller cases like 1 , 0 , etc
// 12. Is it something to with overflow?
// 13. Did you initialized all the variables properly?
// 14. Did you use the formulas correctly?

// STRESS TESTING !!!!!! STRESS TESTING !!!!!
// STRESS Testing Not working?
// Stress test for multiple cases? 
// Stress test for big inputs?
// Stress test for really small inputs?
// Even then if it doesn't work -> Did you wrote the wrong Brute force code


// Check these things if you are not generating ideas
// 1. Did you try thinking it in reverse?
// 2. Read the problem statement again
// 3. Check the constraints again
// 4. Try smaller cases in notebook and try to expand
// 5. Think about invariants
// 6. Think simpler ideas maybe?
// 7. Think brute force and try to get something out of it.
// 8. Maybe take a deep breath and take a break for few minutes and drink some water? :3 
int primes[] = {285897553, 745494041, 693888673, 950758511, 282174533, 847345579, 722520917, 354688703, 963459817, 139793893};
const int MOD1 = primes[3];
const int MOD2 = primes[5];
const int B1 = 359;
const int B2 = 271;
void GG()
{
	int n;
	cin >> n;
	string s;
	cin >> s;
	ll tot = 1LL * n * (n + 1);
	tot /= 2;
	vector<int> cnt(400);
	pair<ll,ll> fhash = {0 , 0};
	auto rhash = fhash;
	// cout << tot << ' ';
	for(int i = n - 1; i >= 0; i--){
		tot -= cnt[s[i]];
		cnt[s[i]]++;
	}
	// cout << tot << ' ';
	// auto fupd = [&](int ind){
	// 	fhash.first = 1LL * fhash.first * B1 % MOD1;
	// 	fhash.first = (fhash.first + s[ind]) % MOD1;
	// 	fhash.second = 1LL * fhash.second * B2 % MOD2;
	// 	fhash.second = (fhash.second + s[ind]) % MOD2;
	// };
	// auto bupd = [&](int ind , int gun1 , int gun2){
	// 	ll x1 = 1LL * s[ind] * gun1 % MOD1;
	// 	ll x2 = 1LL * s[ind] * gun2 % MOD2;
	// 	rhash.first = (rhash.first + x1) % MOD1;
	// 	rhash.second = (rhash.second + x2) % MOD2;
	// };
	// ll x1 = 1 , x2 = 1;
	// for(int i = 0; i < n - 1; i++){
	// 	fupd(0);
	// 	bupd(n - 1 - i , x1 , x2);
	// 	x1 = 1LL * x1 * B1 % MOD1;
	// 	x2 = 1LL * x2 * B2 % MOD2;
	// 	if(fhash == rhash) tot--;
	// }
	cout << tot << endl;
}

signed main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	int ttc=1;
	// cin>>ttc;
	//int cnt=0;
	while(ttc--)
	{
		//cout<<"Case "<<++cnt<<": ";
		GG();
	}
}