import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int n = Integer.parseInt(br.readLine());
		String[] sa = br.readLine().split(" ");
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sa[i]);
		}
		br.close();

		if (n >= 4) {
			PrintWriter pw = new PrintWriter(System.out);
			pw.println(0);
			pw.println("1 2");
			pw.println("1 2");
			for (int i = n - 2; i >= 2; i--) {
				pw.println("1 " + i);
			}
			pw.flush();

		} else {
			Set<Integer> set = new HashSet<>();
			Map<Integer, Integer> map0 = bunkai(a[0]);
			for (Integer k : map0.keySet()) {
				set.add(k);
			}
			long m = a[0];
			for (int i = 1; i < n; i++) {
				Map<Integer, Integer> map = bunkai(a[i]);
				for (Integer k : map.keySet()) {
					if (!set.add(k)) {
						m = 0;
						break;
					}
				}
				if (m != 0) {
					m = (m - 1) * (a[i] - 1);
				}
			}
			System.out.println(m);
			for (int i = 0; i < n - 1; i++) {
				System.out.println("1 2");
			}
			throw new RuntimeException();
		}
	}

	static Map<Integer, Integer> bunkai(int n) {
		Map<Integer, Integer> soinsu = new HashMap<>();
		int end = (int) Math.sqrt(n);
		int d = 2;
		while (n > 1) {
			if (n % d == 0) {
				n /= d;
				soinsu.put(d, soinsu.getOrDefault(d, 0) + 1);
				end = (int) Math.sqrt(n);
			} else {
				if (d > end) {
					d = n - 1;
				}
				d++;
			}
		}
		return soinsu;
	}
}