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

public class Main {
    public static void main(String[] args) {
        PrintWriter out = new PrintWriter(System.out);
        FastScanner sc = new FastScanner();
        Strategy strategy = new MyStrategy();
        strategy.solve(out, sc);
        out.flush();
    }
}

class MyStrategy implements Strategy {
    @Override
    public void solve(PrintWriter out, FastScanner sc) {
        int N = sc.nextInt();
        String S = sc.next();
        boolean[] first = new boolean[10];
        boolean[][] second = new boolean[10][10];
        boolean[][][] third = new boolean[10][10][10];
        Arrays.fill(first, false);
        for (int i=0; i<10; i++) {
            Arrays.fill(second[i], false);
            for (int j=0; j<10; j++) {
                Arrays.fill(third[i][j], false);
            }
        }

        for (int l=0; l<N; l++) {
            int n = Character.getNumericValue(S.charAt(l));
            for (int i=0; i<10; i++) {
                if (first[i]) {
                    for (int j=0; j<10; j++) {
                        if(second[i][j]) {
                            third[i][j][n] = true;
                        }
                    }
                    second[i][n] = true;
                }
            }
            first[n] = true;
        }
        int cnt = 0;
        for (int i=0; i<10; i++) {
            for (int j=0; j<10; j++) {
                for (int k=0; k<10; k++) {
                    if (third[i][j][k]) cnt++;
                }
            }
        }
        out.println(cnt);
    }
}

interface Strategy {
    void solve(PrintWriter out, FastScanner sc);
}

class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    private boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        }else{
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }
    private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
    private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
    public boolean hasNext() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte();}
    public String next() {
        if (!hasNext()) throw new NoSuchElementException();
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while(isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }
    public long nextLong() {
        if (!hasNext()) throw new NoSuchElementException();
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while(true){
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            }else if(b == -1 || !isPrintableChar(b)){
                return minus ? -n : n;
            }else{
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }
    public int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException();
        return (int) nl;
    }
    public double nextDouble() { return Double.parseDouble(next());}
}


Measured memory_bytes: 24148