AtCoder Inc. has decided to lock the door of its office with a 3-digit PIN code.

The company has an N-digit lucky number, S. Takahashi, the president, will erase N-3 digits from S and concatenate the remaining 3 digits without changing the order to set the PIN code.

How many different PIN codes can he set this way?

Both the lucky number and the PIN code may begin with a 0.

Constraints

* 4 \leq N \leq 30000
* S is a string of length N consisting of digits.

Input

Input is given from Standard Input in the following format:


N
S


Output

Print the number of different PIN codes Takahashi can set.

Examples

Input

4
0224


Output

3


Input

6
123123


Output

17


Input

19
3141592653589793238


Output

329
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map.Entry;

import java.util.PriorityQueue;
import java.util.Random;
import java.util.StringTokenizer;
import java.util.TreeSet;

public class Main {
	
	public static void main(String[] args) throws IOException {	
		try(final Scanner sc = new Scanner(System.in)){
			final int N = sc.nextInt();
			final char[] chs = sc.next().toCharArray();
			
			int[] counts = new int[10];
			for(int i = chs.length - 1; i >= 0; i--) {
				counts[chs[i] - '0']++;
			}
			
			HashSet<String> answer = new HashSet<String>();
			
			boolean[] i_pat = new boolean[10];
			boolean[][] j_pat = new boolean[10][10];
			
			for(int i = 0; i < N; i++) {
				final int c1 = chs[i] - '0';
				counts[c1]--;
				
				if(i_pat[c1]) { continue; }
				int[] backup = counts.clone();
				
				for(int j = i + 1; j < N; j++) {
					final int c2 = chs[j] - '0';
					counts[c2]--;
					
					if(j_pat[c1][c2]) { continue; }
					
					for(int val = 0; val < 10; val++) {
						if(counts[val] <= 0) { continue; }
						
						answer.add(c1 + "" + c2 + "" + val);
					}
					
					j_pat[c1][c2] = true;
				}
				
				i_pat[c1] = true;
				counts = backup;
			}
			
			System.out.println(answer.size());
			
		}
	}

	public static class Scanner implements Closeable {
		private BufferedReader br;
		private StringTokenizer tok;

		public Scanner(InputStream is) throws IOException {
			br = new BufferedReader(new InputStreamReader(is));
		}

		private void getLine() throws IOException {
			while(!hasNext()){
				tok = new StringTokenizer(br.readLine());
			}
		}

		private boolean hasNext() {
			return tok != null && tok.hasMoreTokens();
		}

		public String next() throws IOException {
			getLine();
			return tok.nextToken();
		}

		public int nextInt() throws IOException {
			return Integer.parseInt(next());
		}

		public long nextLong() throws IOException {
			return Long.parseLong(next());
		}
		

		public double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int n) throws IOException {
			final int[] ret = new int[n];
			for(int i = 0; i < n; i++){
				ret[i] = this.nextInt();
			}
			return ret;
		}

		public long[] nextLongArray(int n) throws IOException {
			final long[] ret = new long[n];
			for(int i = 0; i < n; i++){
				ret[i] = this.nextLong();
			}
			return ret;
		}

		public void close() throws IOException {
			br.close();
		}
	}
}