// Slower C++ solution:
#include <bits/stdc++.h>

using namespace std;

#define rep(i,N) for(int i=0;i<int(N);++i)

#define rep1(i,N) for(int i=1;i<int(N);++i)

#define all(a) (a).begin(),(a).end()

#define print(v) { cerr<<#v<<": [ "; for(auto _ : v) cerr<<_<<", "; cerr<<"]"<<endl; }

#define printpair(v) { cerr<<#v<<": [ "; for(auto _ : v) cerr<<"{"<<_.first<<","<<_.second<<"}"<<", "; cerr<<"]"<<endl; }



typedef long long ll;



template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }



const int INF = 1e9;

const ll INFLL = 1e18;

const ll MOD = 1e9+7;

const double PI = acos(-1.0);



const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};

const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};



/*------------------------------------/

for library*/



/*------------------------------------*/



int main() {

    cin.tie(0);

    ios::sync_with_stdio(false);

    cout << fixed << setprecision(20);



    int N;

    string S;

    cin>>N>>S;

    set<string> set1pre,set2pre,set3;

    string y = "";

    y.push_back(S[0]);

    set1pre.insert(y);

    rep1(i,N){

        set<string> set1,set2;

        string xx = "";

        xx.push_back(S[i]);

        set1.insert(xx);

        for(auto x1:set1pre){

            set1.insert(x1);

            x1.push_back(S[i]);

            set2.insert(x1);

        }

        for(auto x2:set2pre){

            set2.insert(x2);

            x2.push_back(S[i]);

            set3.insert(x2);

        }

        swap(set1pre,set1);

        swap(set2pre,set2);

    }

    /*

    for(auto x:set1pre){

        cerr<<x<<endl;

    }

    cerr<<endl;

    for(auto x:set2pre){

        cerr<<x<<endl;

    }

    cerr<<endl;

    for(auto x:set3){

        cerr<<x<<endl;

    }

    cerr<<endl;

    */

    cout<<set3.size()<<endl;



}

// Faster C++ solution for the same problem (measured speedup: 1.1912139569128741x):
#include <bits/stdc++.h>

using namespace std;

#define rep(i,N) for(int i=0;i<int(N);++i)

#define rep1(i,N) for(int i=1;i<int(N);++i)

#define all(a) (a).begin(),(a).end()

#define print(v) { cerr<<#v<<": [ "; for(auto _ : v) cerr<<_<<", "; cerr<<"]"<<endl; }

#define printpair(v) { cerr<<#v<<": [ "; for(auto _ : v) cerr<<"{"<<_.first<<","<<_.second<<"}"<<", "; cerr<<"]"<<endl; }



typedef long long ll;



template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }

template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }



const int INF = 1e9;

const ll INFLL = 1e18;

const ll MOD = 1e9+7;

const double PI = acos(-1.0);



const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};

const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};



/*------------------------------------/

for library*/



/*------------------------------------*/



int main() {

    cin.tie(0);

    ios::sync_with_stdio(false);

    cout << fixed << setprecision(20);



    int N;string S;

    cin>>N>>S;

    int ans = 0;

    rep(i,10)rep(j,10)rep(k,10){

        int cnt = 0;

        rep(l,N){

            if      (cnt  == 0 && i == S[l]-'0')cnt++;

            else if (cnt  == 1 && j == S[l]-'0')cnt++;

            else if (cnt  == 2 && k == S[l]-'0')cnt++;

        }

        if(cnt==3)ans++;

    }

    cout<<ans<<endl;

}