import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.SortedSet;
import java.util.StringTokenizer;
import java.util.TreeSet;

/**
 * <b> Algorithm on Codeforces. Problem C div 2 </b> </br>
 * @author Huynh Quang Thao
 *
 */
public class Main {

    public static void main(String[] args) throws Exception {
        Main main = new Main();
        main.run();
    }

    public void run() throws Exception {
         Scanner sc = null;
         PrintWriter pr = null;

         pr=new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
         sc = new Scanner(new BufferedReader(new InputStreamReader(System.in)));
         sc = new Scanner(new File("input.txt"));

         int n = sc.nextInt();
         Map<Integer, ArrayList<Integer>> map = new HashMap<>();
         for (int i = 1; i <= n; i++) {
             int key = sc.nextInt();
             if (map.containsKey(key)) {
                 ArrayList<Integer> value = map.get(key);
                 value.add(i);
                 map.put(key, value);
             }
             else {
                 ArrayList<Integer> value = new ArrayList<>();
                 value.add(i);
                 map.put(key, value);
             }
         }

         // process
         SortedSet<Integer> keys = new TreeSet<Integer>(map.keySet());
         int count = 0;
         StringBuilder sb = new StringBuilder();
         for (Integer key : keys) {
             ArrayList<Integer> values = map.get(key);
             if (values.size() == 1) {
                 //sb.append("%d %d\n", key, 0);
                 sb.append(key + " " + 0 + "\n");
                 count++;
             }
             else if (check(values)) {
                 sb.append(key + " " + (values.get(1) - values.get(0))  + "\n");
                 //sb.append("%d %d\n", key, values.get(1) - values.get(0));
                 count++;
             }
         }

         System.out.println(count);
         System.out.println(sb.toString());


         pr.close();
         sc.close();
    }

    public boolean check(ArrayList<Integer> list) {
        // assume size >= 2
        int d = list.get(1) - list.get(0);
        for (int i = 1; i < list.size(); i++) {
            if (list.get(i) - list.get(i-1) != d) return false;
        }
        return true;
    }

    static class InputReader {
        public BufferedReader reader;

        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream));
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                }
                catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

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

        public float nextFloat() {
            return Float.parseFloat(next());
        }

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

        public BigInteger nextBigInteger() {
            return new BigInteger(next());
        }

    }
}