import java.io.*;
import java.io.IOException;
import java.util.*;

class Main {
    final static int INF = 1 << 28;
    final static long LNF = 1L << 60;
    final static double EPS = 1e-9;
    final static double GOLDEN_RATIO = (1.0 + Math.sqrt(5)) / 2.0;

    static final long MOD = 1_000_000_007;

    public static void main(String[] args) throws Exception {
        final MyScanner sc = new MyScanner();
        long N;
        N = sc.nextLong();
        String S;
        S = sc.next();
        solve(N, S);
    }


    static void solve(long N, String S){
        int[][][] tbl = new int[11][11][11];

        for (int[][] is : tbl) {
            for (int[] is2 : is) {
                Arrays.fill(is2, 0);
            }
        }
        for (char c : S.toCharArray()) {
            int c1 = Character.getNumericValue(c);
            c1++;

            for (int i = 1; i <= 10; i++) {
                for (int j = 1; j <= 10; j++) {
                    tbl[i][j][c1] |= tbl[i][j][0];
                }
            }
            for (int i = 1; i <= 10; i++) {
                tbl[i][c1][0] |= tbl[i][0][0];
            }
            for (int i = 1; i <= 10; i++) {
                tbl[c1][0][0] = 1;
            }
        }

        long ans = 0;
        for (int i = 1; i <= 10; i++) {
            for (int j = 1; j <= 10; j++) {
                for (int k = 1; k <= 10; k++) {
                    ans += tbl[i][j][k];
                }
            }
        }
        System.out.println(ans);


    }


    static class MyScanner {
 
        BufferedReader br;
        StringTokenizer st;
 
        MyScanner(FileReader fileReader) {
            br = new BufferedReader(fileReader);
        }
 
        MyScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
 
        String nn() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
 
        String next() {
            String ans = "";
            try {
                ans = br.readLine();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
            return ans;
        }
 
        char nextChar() {
            return nn().charAt(0);
        }
 
        int nextInt() {
            return Integer.parseInt(nn());
        }
 
        long nextLong() {
            return Long.parseLong(nn());
        }
 
        double nextDouble() {
            return Double.parseDouble(nn());
        }
 
        Integer[] niArr0(int n) {
            Integer[] ar = new Integer[n];
            for (int i = 0; i < n; i++) {
                ar[i] = nextInt();
            }
            return ar;
        }
 
        Integer[] niArr1(int n) {
            Integer[] ar = new Integer[n + 1];
            for (int i = 1; i <= n; i++) {
                ar[i] = nextInt();
            }
            return ar;
        }
 
        Long[] nlArr0(int n) {
            Long[] ar = new Long[n];
            for (int i = 0; i < n; i++) {
                ar[i] = nextLong();
            }
            return ar;
        }
 
        Long[] nlArr1(int n) {
            Long[] ar = new Long[n + 1];
            for (int i = 1; i <= n; i++) {
                ar[i] = nextLong();
            }
            return ar;
        }
    }

}


Measured memory_bytes: 24132