#include "bits/stdc++.h"

#define rep(loop, N) for (int loop = 0; loop < N; loop++)
using namespace std;

struct Node {
	Node* parent = NULL;
	vector<Node*> child;
	long long value = 0;
};
struct Edge {
	int parent = 0;
	int child = 0;
	bool operator <(const Edge& right) const { return parent < right.parent; }
};
struct Tree {
	vector<Node> node;
	Tree(int, vector<Edge>);
};
Tree::Tree(int nodeNum, vector<Edge> edge) {
	node.resize(nodeNum);
	for (Edge& it : edge) {
		node[it.child].parent = &node[it.parent];
		node[it.parent].child.push_back(&node[it.child]);
	}
}

map<long long, int> factorization(long long N) {
	map<long long, int> re;
	while (true) {
		if (N % 2 == 0) {
			N /= 2;
			re[2]++;
			if (N == 1) break;
		}
		else {
			break;
		}
	}
	for (int loop = 3; (long long)loop * (long long)loop <= N; loop += 2) {
		if (N % loop == 0) {
			N /= loop;
			re[loop]++;
			loop -= 2;
			if (N == 1) break;
		}
	}
	if (N > 1) re[N]++;
	return re;
}

struct Memo {
	long long fact = 0;
	long long fact_inv = 0;
	long long inv = 0;
};
class Combination1 {
private:
	long long m_module = 1000000007;
	vector<struct Memo> memo;
public:
	long long calculate(int, int);
	Combination1(int, long long);
};
long long Combination1::calculate(int n, int k) {
	return ((memo[n].fact * memo[k].fact_inv) % m_module * memo[n - k].fact_inv) % m_module;
}
Combination1::Combination1(int memo_max, long long module = 1000000007) {
	m_module = module;
	memo.push_back({ 1,1,0 });
	memo.push_back({ 1,1,1 });
	for (int loop = 2; loop <= memo_max; loop++) {
		struct Memo temp;
		temp.fact = (memo[loop - 1].fact * loop) % m_module;
		temp.inv = m_module - (memo[m_module % loop].inv * int(m_module / loop)) % m_module;
		temp.fact_inv = (memo[loop - 1].fact_inv * temp.inv) % m_module;
		memo.push_back(temp);
	}
}

class Combination2 {
private:
	int size = 0;
	bool add(int);
public:
	vector<int> sequence;
	bool next_combination(void);
	Combination2(int, int);
};
bool Combination2::add(int index) {
	if (index == (int)sequence.size() - 1 && sequence[index] == size - 1
		|| index < (int)sequence.size() - 1 && sequence[index] == sequence[index + 1] - 1) {
		if (index == 0) {
			return false;
		}
		else {
			bool re = add(index - 1);
			sequence[index] = sequence[index - 1] + 1;
			return re;
		}
	}
	else {
		sequence[index]++;
		return true;
	}
}
bool Combination2::next_combination(void) {
	return (sequence.size() == 0) ? false : add(sequence.size() - 1);
}
Combination2::Combination2(int n, int r) {
	size = n;
	for (int loop = 0; loop < r; loop++) sequence.push_back(loop);
	return;
}

void A_November_30(void) {

	int M1, D1, M2, D2; cin >> M1 >> D1 >> M2 >> D2;

	cout << (M1 != M2 ? 1 : 0) << endl;
	return;
}

void B_Tax_Rate(void) {

	int N; cin >> N;

	for (int X = int(N / 1.08); X <= N; X++) {
		if (int(X * 1.08) == N) {
			cout << X << endl;
			return;
		}
	}
	cout << ":(" << endl;
	return;
}

void C_100_to_105(void) {

	int X; cin >> X;
	
	cout << (X % 100 <= X / 100 * 5) << endl;
	return;
}

void D_Lucky_PIN(void) {

	int N; cin >> N;
	string S; cin >> S;

	vector<int> lucky(N);
	rep(index, N) lucky[index] = S[index] - '0';

	int counter = 0;
	rep(target, 10) {
		
		vector<bool> first(10), third(10);
		vector<vector<bool>> pin(10, vector<bool>(10));
		int start = distance(lucky.begin(), find(lucky.begin(), lucky.end(), target));
		
		rep(index, start) first[lucky[index]] = true;
		for (int index = start + 1; index < N; index++) {
			third[lucky[index]] = true;
			if (lucky[index] == target || index == N - 1) {
				rep(loop1, 10) {
					if (first[loop1]) {
						rep(loop2, 10) {
							if (!pin[loop1][loop2]) pin[loop1][loop2] = third[loop2];
						}
					}
					else {
						first[loop1] = third[loop1];
					}
				}
				fill(third.begin(), third.end(), false);
			}
		}
		for (vector<bool>it : pin) {
			for (bool it2 : it) {
				if (it2) counter++;
			}
		}
	}

	cout << counter << endl;
	return;
}

int main(void) {

	//A_November_30();
	//B_Tax_Rate();
	//C_100_to_105();
	D_Lucky_PIN();
	return 0;
}


Measured memory_bytes: 384