using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var a = NList;
        var xor = a.Aggregate((l, r) => l ^ r);
        var list = new Pair[n];
        for (var i = 0; i < n; ++i) list[i] = new Pair(i + 1, a[i]);
        var q = new PriorityQueue<Pair>(n, true);
        for (var i = 0; i < n; ++i) q.Enqueue(list[i]);
        var late = xor == 0;
        WriteLine(late ? "0" : "1");
        while (true)
        {
            if (!late)
            {
                while (q.List[0].Edited)
                {
                    var mv = q.Dequeue();
                    mv.Edited = false;
                    q.Enqueue(mv);
                }
                {
                    var mv = q.Dequeue();
                    var rm = 0;
                    if (xor == mv.Val)
                    {
                        rm = mv.Val;
                        mv.Val = 0;
                        xor = 0;
                    }
                    else
                    {
                        while (xor > 0)
                        {
                            for (var i = 0; i < 20; ++i)
                            {
                                if ((xor & (1 << i)) != 0)
                                {
                                    rm += 1 << i;
                                    xor = xor ^ mv.Val ^ (mv.Val - (1 << i));
                                    mv.Val -= 1 << i;
                                    break;
                                }
                            }
                        }
                    }
                    WriteLine($"{mv.Pos} {rm}");
                    q.Enqueue(mv);
                }
                var ret = NN;
                if (ret < 0) return;
            }
            {
                var c = NList;
                var i = c[0] - 1;
                var k = c[1];
                xor = xor ^ list[i].Val ^ (list[i].Val - k);
                list[i].Val -= k;
                list[i].Edited = true;
                late = false;
                var ret = NN;
                if (ret < 0) return;
            }
        }
    }
    class Pair : IComparable<Pair>
    {
        public int Pos;
        public int Val;
        public bool Edited;
        public Pair(int pos, int val)
        {
            Pos = pos; Val = val;
        }
        public int CompareTo(Pair b)
        {
            return Val.CompareTo(b.Val);
        }
    }
    class PriorityQueue<T> where T : IComparable<T>
    {
        public T[] List;
        public int Count;
        bool IsTopMax;
        public PriorityQueue(int count, bool isTopMax)
        {
            IsTopMax = isTopMax;
            List = new T[Math.Max(128, count)];
        }
        public void Enqueue(T value)
        {
            if (Count == List.Length)
            {
                var newlist = new T[List.Length * 2];
                for (var i = 0; i < List.Length; ++i) newlist[i] = List[i];
                List = newlist;
            }
            var pos = Count;
            List[pos] = value;
            ++Count;
            while (pos > 0)
            {
                var parent = (pos - 1) / 2;
                if (Calc(List[parent], List[pos], true)) break;
                Swap(parent, pos);
                pos = parent;
            }
        }
        public T Dequeue()
        {
            --Count;
            Swap(0, Count);
            var pos = 0;
            while (true)
            {
                var child = pos * 2 + 1;
                if (child >= Count) break;
                if (child + 1 < Count && Calc(List[child + 1], List[child], false)) ++child;
                if (Calc(List[pos], List[child], true)) break;
                Swap(pos, child);
                pos = child;
            }
            return List[Count];
        }
        bool Calc(T a, T b, bool equalVal)
        {
            var ret = a.CompareTo(b);
            if (ret == 0 && equalVal) return true;
            return IsTopMax ? ret > 0 : ret < 0;
        }
        void Swap(int a, int b)
        {
            var tmp = List[a];
            List[a] = List[b];
            List[b] = tmp;
        }
    }
}