using System;
using System.Collections.Generic;
using System.Linq;

// https://yukicoder.me/problems/no/2565
class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("4 6");
            WillReturn.Add("1 2");
            WillReturn.Add("2 4");
            WillReturn.Add("2 3");
            WillReturn.Add("3 1");
            WillReturn.Add("3 4");
            WillReturn.Add("4 3");
            //4
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("3 3");
            WillReturn.Add("1 2");
            WillReturn.Add("3 1");
            WillReturn.Add("2 1");
            //-1
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("7 12");
            WillReturn.Add("1 2");
            WillReturn.Add("1 4");
            WillReturn.Add("1 5");
            WillReturn.Add("2 5");
            WillReturn.Add("3 1");
            WillReturn.Add("3 2");
            WillReturn.Add("4 1");
            WillReturn.Add("4 6");
            WillReturn.Add("5 1");
            WillReturn.Add("5 6");
            WillReturn.Add("6 7");
            WillReturn.Add("7 3");
            //5
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static int mN;

    // 隣接リスト
    static Dictionary<int, List<int>> mToNodeListDict = new Dictionary<int, List<int>>();

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(pX => int.Parse(pX)).ToArray();

        SplitAct(InputList[0]);
        mN = wkArr[0];

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            int FromNode = wkArr[0];
            int ToNode = wkArr[1];

            if (mToNodeListDict.ContainsKey(FromNode) == false) {
                mToNodeListDict[FromNode] = new List<int>();
            }
            mToNodeListDict[FromNode].Add(ToNode);
        }

        var AnswerList = new List<int>();

        bool Result1, Result2, Result3;
        int Cost1 = ExecBFS(out Result1, 1, 3);
        int Cost2 = ExecBFS(out Result2, 3, 4);
        int Cost3 = ExecBFS(out Result3, 4, 1);
        if (Result1 && Result2 && Result3) {
            AnswerList.Add(Cost1 + Cost2 + Cost3);
        }

        Cost1 = ExecBFS(out Result1, 1, 4);
        Cost2 = ExecBFS(out Result2, 4, 3);
        Cost3 = ExecBFS(out Result3, 3, 1);
        if (Result1 && Result2 && Result3) {
            AnswerList.Add(Cost1 + Cost2 + Cost3);
        }

        if (AnswerList.Count > 0) {
            Console.WriteLine(AnswerList.Min());
        }
        else {
            Console.WriteLine(-1);
        }
    }

    // 始点と終点を引数として、コストを返す
    static int ExecBFS(out bool pHasAnswer, int pStaNode, int pGoalNode)
    {
        //Console.WriteLine("pStaNode={0},pGoalNode={1}", pStaNode, pGoalNode);
        pHasAnswer = false;

        var VisitedSet = new HashSet<int>();
        VisitedSet.Add(pStaNode);

        var Que = new Queue<JyoutaiDef>();
        JyoutaiDef WillEnqueue;
        WillEnqueue.CurrNode = pStaNode;
        WillEnqueue.Level = 0;
        Que.Enqueue(WillEnqueue);

        while (Que.Count > 0) {
            JyoutaiDef Dequeued = Que.Dequeue();
            //Console.WriteLine("CurrNode={0}", Dequeued.CurrNode);

            if (Dequeued.CurrNode == pGoalNode) {
                pHasAnswer = true;
                return Dequeued.Level;
            }

            if (mToNodeListDict.ContainsKey(Dequeued.CurrNode)) {
                foreach (int EachToNode in mToNodeListDict[Dequeued.CurrNode]) {
                    if (VisitedSet.Add(EachToNode)) {
                        WillEnqueue.CurrNode = EachToNode;
                        WillEnqueue.Level = Dequeued.Level + 1;
                        Que.Enqueue(WillEnqueue);
                    }
                }
            }
        }
        return int.MaxValue;
    }

    struct JyoutaiDef
    {
        internal int CurrNode;
        internal int Level;
    }
}