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());
                }

        }
}