#region いつもの
using System;
using System.Collections.Generic;
using System.Linq;
using ConsoleReader = AtCoderProject.Reader.ConsoleReader;
using IEnumerable = System.Collections.IEnumerable;
using IEnumerator = System.Collections.IEnumerator;
using BigInteger = System.Numerics.BigInteger;
using TextReader = System.IO.TextReader;
using StringBuilder = System.Text.StringBuilder;
using static Global;
using static NumGlobal;

static class Global
{
    public static void Swap<T>(ref T a, ref T b) { T tmp = a; a = b; b = tmp; }
    public static T[] NewArray<T>(int len0, T value) => new T[len0].Fill(value);
    public static T[] NewArray<T>(int len0, Func<T> factory)
    {
        var arr = new T[len0];
        for (int i = 0; i < arr.Length; i++) arr[i] = factory();
        return arr;
    }
    public static T[][] NewArray<T>(int len0, int len1, T value) where T : struct
    {
        var arr = new T[len0][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, value);
        return arr;
    }
    public static T[][] NewArray<T>(int len0, int len1, Func<T> factory)
    {
        var arr = new T[len0][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, factory);
        return arr;
    }
    public static T[][][] NewArray<T>(int len0, int len1, int len2, T value) where T : struct
    {
        var arr = new T[len0][][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, value);
        return arr;
    }
    public static T[][][] NewArray<T>(int len0, int len1, int len2, Func<T> factory)
    {
        var arr = new T[len0][][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, factory);
        return arr;
    }
    public static T[][][][] NewArray<T>(int len0, int len1, int len2, int len3, T value) where T : struct
    {
        var arr = new T[len0][][][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, len3, value);
        return arr;
    }
    public static T[][][][] NewArray<T>(int len0, int len1, int len2, int len3, Func<T> factory)
    {
        var arr = new T[len0][][][];
        for (int i = 0; i < arr.Length; i++) arr[i] = NewArray(len1, len2, len3, factory);
        return arr;
    }
    private class ComparerReverseImpl<T> : Comparer<T> where T : IComparable<T> { public override int Compare(T y, T x) => x.CompareTo(y); public override bool Equals(object obj) => obj != null && GetType() == obj.GetType(); public override int GetHashCode() => GetType().GetHashCode(); }
    public static IComparer<T> ComparerReverse<T>() where T : IComparable<T> => new ComparerReverseImpl<T>();
    public static string AllLines<T>(IEnumerable<T> source) => string.Join("\n", source);
    public static string AllJoin<T>(IEnumerable<T> source) => string.Join(" ", source);
}
static class NumGlobal
{
    public static int Pow(int x, int y)
    {
        int res = 1;
        for (; y > 0; y >>= 1)
        {
            if ((y & 1) == 1) res *= x;
            x *= x;
        }
        return res;
    }
    public static BigInteger ParseBigInteger(string s)
    {
        // 自前実装の方が速い
        var res = BigInteger.Zero;
        var splited = new string[(s.Length + 7) / 8];
        for (var i = 0; i < splited.Length - 1; i++)
        {
            splited[i] = s.Substring(8 * i, 8);
        }
        splited[splited.Length - 1] = s.Substring(8 * (splited.Length - 1));
        foreach (var sp in splited)
        {
            res *= (int)Math.Pow(10, sp.Length);
            res += int.Parse(sp);
        }
        return res;
    }
    public static int BitCount(int x) { x -= (x >> 1) & 0x55555555; x = (x & 0x33333333) + ((x >> 2) & 0x33333333); x = (x + (x >> 4)) & 0x0f0f0f0f; x += x >> 8; x += x >> 16; return x & 0x3f; }
    public static int BitCount(long x) { x -= (x >> 1) & 0x5555555555555555; x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333); x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f; x += x >> 8; x += x >> 16; x += x >> 32; return (int)(x & 0x0000007f); }
    public static int MSB(int x) { x |= x >> 1; x |= x >> 2; x |= x >> 4; x |= x >> 8; x |= x >> 16; return BitCount(x) - 1; }
    public static int MSB(long x) { x |= x >> 1; x |= x >> 2; x |= x >> 4; x |= x >> 8; x |= x >> 16; x |= x >> 32; return BitCount(x) - 1; }
    public static int LSB(int x) { x |= x << 1; x |= x << 2; x |= x << 4; x |= x << 8; x |= x << 16; return 32 - BitCount(x); }
    public static int LSB(long x) { x |= x << 1; x |= x << 2; x |= x << 4; x |= x << 8; x |= x << 16; x |= x << 32; return 64 - BitCount(x); }
}
static class Ext
{
    public static long ToLong(this int i) => i;
    public static T[] Fill<T>(this T[] arr, T value)
    {
        for (var i = 0; i < arr.Length; i++) arr[i] = value;
        return arr;
    }
    public static T[] Sort<T>(this T[] arr) { Array.Sort(arr); return arr; }
    public static string[] Sort(this string[] arr) => Sort(arr, StringComparer.OrdinalIgnoreCase);
    public static T[] Sort<T, U>(this T[] arr, Func<T, U> selector) where U : IComparable<U> => Sort(arr, (a, b) => selector(a).CompareTo(selector(b)));
    public static T[] Sort<T>(this T[] arr, Comparison<T> comparison) { Array.Sort(arr, comparison); return arr; }
    public static T[] Sort<T>(this T[] arr, IComparer<T> comparer) { Array.Sort(arr, comparer); return arr; }
    public static T[] Reverse<T>(this T[] arr) { Array.Reverse(arr); return arr; }
    public static Tuple<int, T> MaxBy<T>(this T[] arr) where T : IComparable<T>
    {
        T max = arr[0];
        int maxIndex = 0;
        for (int i = 0; i < arr.Length; i++)
        {
            if (max.CompareTo(arr[i]) < 0)
            {
                max = arr[i];
                maxIndex = i;
            }
        }
        return Tuple.Create(maxIndex, max);
    }
    public static Tuple<TSource, TMax> MaxBy<TSource, TMax>
        (this IEnumerable<TSource> source, Func<TSource, TMax> maxBySelector)
        where TMax : IComparable<TMax>
    {
        TMax max;
        TSource maxByItem;

        var e = source.GetEnumerator();
        e.MoveNext();
        maxByItem = e.Current;
        max = maxBySelector(maxByItem);
        while (e.MoveNext())
        {
            var item = e.Current;
            var next = maxBySelector(item);
            if (max.CompareTo(next) < 0)
            {
                max = next;
                maxByItem = item;
            }
        }
        return Tuple.Create(maxByItem, max);
    }
    public static Tuple<int, T> MinBy<T>(this T[] arr) where T : IComparable<T>
    {
        T min = arr[0];
        int minIndex = 0;
        for (int i = 0; i < arr.Length; i++)
        {
            if (min.CompareTo(arr[i]) > 0)
            {
                min = arr[i];
                minIndex = i;
            }
        }
        return Tuple.Create(minIndex, min);
    }
    public static Tuple<TSource, TMin> MinBy<TSource, TMin>
        (this IEnumerable<TSource> source, Func<TSource, TMin> minBySelector)
        where TMin : IComparable<TMin>
    {
        TMin min;
        TSource minByItem;

        var e = source.GetEnumerator();
        e.MoveNext();
        minByItem = e.Current;
        min = minBySelector(minByItem);
        while (e.MoveNext())
        {
            var item = e.Current;
            var next = minBySelector(item);
            if (min.CompareTo(next) > 0)
            {
                min = next;
                minByItem = item;
            }
        }
        return Tuple.Create(minByItem, min);
    }
    public static IEnumerable<TSource> Append<TSource>(this IEnumerable<TSource> source, TSource element)
    {
        foreach (var item in source)
            yield return item;
        yield return element;
    }
    public static IEnumerable<TSource> Prepend<TSource>(this IEnumerable<TSource> source, TSource element)
    {
        yield return element;
        foreach (var item in source)
            yield return item;
    }
    public static IComparer<T> Reverse<T>(this IComparer<T> comparer) => Comparer<T>.Create((x, y) => comparer.Compare(y, x));
    public static Dictionary<TKey, int> GroupCount<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) => source.GroupBy(keySelector).ToDictionary(g => g.Key, g => g.Count());
    public static Dictionary<TKey, int> GroupCount<TKey>(this IEnumerable<TKey> source) => source.GroupCount(i => i);
    public static TValue Get<TKey, TValue>(this Dictionary<TKey, TValue> dic, TKey key)
    {
        TValue v;
        dic.TryGetValue(key, out v);
        return v;
    }
    public static TValue GetOrInit<TKey, TValue>(this Dictionary<TKey, TValue> dic, TKey key, TValue value)
    {
        TValue v;
        if (dic.TryGetValue(key, out v))
            return v;
        return dic[key] = value;
    }
}
class ΔDebugView<T> { private IEnumerable<T> collection; public ΔDebugView(IEnumerable<T> collection) { if (collection == null) throw new ArgumentNullException(nameof(collection)); this.collection = collection; }[System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.RootHidden)] public T[] Items => collection.ToArray(); }
namespace AtCoderProject.Reader
{
    using System.IO;
    using System.Text;
    using System.Diagnostics;
    using System.Runtime.CompilerServices;
#pragma warning disable CA1819
    [DebuggerNonUserCode]
    public class ConsoleReader
    {
        const int BufSize = 1 << 12;
        private readonly byte[] buffer = new byte[BufSize];
        private readonly Stream input;
        private readonly Encoding encoding;
        private int pos = 0;
        private int len = 0;
        public ConsoleReader(Stream input, Encoding encoding) { this.input = input; this.encoding = encoding; }
        public ConsoleReader(Stream input) : this(input, Encoding.UTF8) { }
        public ConsoleReader(string text) : this(new MemoryStream(Encoding.UTF8.GetBytes(text))) { }
        private void MoveNext() { if (++pos >= len) { len = input.Read(buffer, 0, buffer.Length); if (len == 0) { buffer[0] = 10; } pos = 0; } }

        public int Int
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                int res = 0;
                bool neg = false;
                while (buffer[pos] < 48) { neg = buffer[pos] == 45; MoveNext(); }
                do { res = res * 10 + (buffer[pos] ^ 48); MoveNext(); } while (48 <= buffer[pos]);
                return neg ? -res : res;
            }
        }
        public int Int0 => this.Int - 1;
        public long Long
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                long res = 0;
                bool neg = false;
                while (buffer[pos] < 48) { neg = buffer[pos] == 45; MoveNext(); }
                do { res = res * 10 + (buffer[pos] ^ 48); MoveNext(); } while (48 <= buffer[pos]);
                return neg ? -res : res;
            }
        }
        public long Long0 => this.Long - 1;
        public string String
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                var sb = new List<byte>();
                while (buffer[pos] <= 32) MoveNext();
                do { sb.Add(buffer[pos]); MoveNext(); } while (32 < buffer[pos]);
                return this.encoding.GetString(sb.ToArray());
            }
        }
        public string Ascii
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                var sb = new StringBuilder();
                while (buffer[pos] <= 32) MoveNext();
                do { sb.Append((char)buffer[pos]); MoveNext(); } while (32 < buffer[pos]);
                return sb.ToString();
            }
        }
        public string Line
        {
            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            get
            {
                var sb = new List<byte>();
                while (buffer[pos] < 32) MoveNext();
                do { sb.Add(buffer[pos]); MoveNext(); } while (buffer[pos] != 10 && buffer[pos] != 13);
                return this.encoding.GetString(sb.ToArray());
            }
        }
        public double Double => double.Parse(this.Ascii);

        [DebuggerNonUserCode]
        public struct RepeatReader
        {
            ConsoleReader cr;
            int count;
            public RepeatReader(ConsoleReader cr, int count) { this.cr = cr; this.count = count; }
            public T[] Select<T>(Func<ConsoleReader, T> factory) { var arr = new T[count]; for (var i = 0; i < count; i++) arr[i] = factory(cr); return arr; }
            public string[] Line { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.Line; return arr; } }
            public string[] String { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.String; return arr; } }
            public string[] Ascii { get { var arr = new string[count]; for (var i = 0; i < count; i++) arr[i] = cr.Ascii; return arr; } }
            public int[] Int { get { var arr = new int[count]; for (var i = 0; i < count; i++) arr[i] = cr.Int; return arr; } }
            public int[] Int0 { get { var arr = new int[count]; for (var i = 0; i < count; i++) arr[i] = cr.Int0; return arr; } }
            public long[] Long { get { var arr = new long[count]; for (var i = 0; i < count; i++) arr[i] = cr.Long; return arr; } }
            public long[] Long0 { get { var arr = new long[count]; for (var i = 0; i < count; i++) arr[i] = cr.Long0; return arr; } }
            public double[] Double { get { var arr = new double[count]; for (var i = 0; i < count; i++) arr[i] = cr.Double; return arr; } }
        }
        public RepeatReader Repeat(int count) => new RepeatReader(this, count);

        [DebuggerNonUserCode]
        public struct SplitReader
        {
            ConsoleReader cr;
            public SplitReader(ConsoleReader cr) { this.cr = cr; }
            public string[] String { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<string>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.String); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public string[] Ascii { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<string>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Ascii); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public int[] Int { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<int>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Int); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public int[] Int0 { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<int>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Int0); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public long[] Long { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<long>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Long); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public long[] Long0 { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<long>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Long0); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
            public double[] Double { get { while (cr.buffer[cr.pos] <= 32) cr.MoveNext(); var list = new List<double>(); do { if (cr.buffer[cr.pos] < 32) cr.MoveNext(); else list.Add(cr.Double); } while (cr.buffer[cr.pos] != 10 && cr.buffer[cr.pos] != 13); return list.ToArray(); } }
        }
        public SplitReader Split => new SplitReader(this);
    }
}
public class Program
{
    [System.Diagnostics.DebuggerBrowsable(System.Diagnostics.DebuggerBrowsableState.Never)] private ConsoleReader cr;

    public Program(ConsoleReader consoleReader) { this.cr = consoleReader; }
    static void Main() => Console.WriteLine(new Program(new ConsoleReader(Console.OpenStandardInput())).Result());
    #endregion
    public string Result() { var obj = Calc(); if (obj is bool) return (bool)obj ? "YES" : "NO"; if (obj is double) return ((double)obj).ToString("0.####################"); return obj.ToString(); }
    private object Calc()
    {
        N = cr.Int;
        var gb = new GraphBuilder(1 + N * (N - 1) / 2, true);
        var arrs = cr.Repeat(N).Select(cr => cr.Repeat(N - 1).Int0);

        for (int i = 0; i < N; i++)
        {
            var prev = MatchIndex(arrs[i][0], i);
            gb.Add(0, prev);
            for (int j = 1; j < N - 1; j++)
            {
                var n = MatchIndex(arrs[i][j], i);
                gb.Add(prev, n);
                prev = n;
            }
        }
        graph = gb.ToArray();
        res = new int[graph.Length];
        st = new Status[graph.Length];
        try
        {
            return Dfs(0);
        }
        catch
        {
            return -1;
        }
    }

    int Dfs(int i)
    {
        if (st[i] == Status.Done) return res[i];
        st[i] = Status.Active;
        foreach (var child in graph[i].children)
        {
            if (st[child] == Status.Active) throw new Exception("閉路検出");
            res[i] = Math.Max(res[i], Dfs(child) + 1);
        }
        st[i] = Status.Done;
        return res[i];
    }

    int[] res;
    Status[] st;
    Node[] graph;

    int N;
    int MatchIndex(int i, int j)
    {
        if (j < i) Swap(ref i, ref j);
        return j + i * (N - 1) - i * (i + 1) / 2;
    }
}
enum Status
{
    None,
    Active,
    Done
}
class GraphBuilder
{
    private List<int>[] roots;
    private List<int>[] children;
    public GraphBuilder(int count, bool isOriented)
    {
        this.roots = new List<int>[count];
        this.children = new List<int>[count];
        for (var i = 0; i < count; i++)
        {
            if (isOriented)
            {
                this.roots[i] = new List<int>();
                this.children[i] = new List<int>();
            }
            else
            {
                this.roots[i] = this.children[i] = new List<int>();
            }
        }
    }
    public GraphBuilder(int count, ConsoleReader cr, int edgeCount, bool isOriented) : this(count, isOriented)
    {
        for (var i = 0; i < edgeCount; i++)
            this.Add(cr.Int0, cr.Int0);
    }
    public void Add(int from, int to)
    {
        children[from].Add(to);
        roots[to].Add(from);
    }
    public TreeNode[] ToTree(int root)
    {
        if (this.roots[0] != this.children[0]) throw new Exception("木には無向グラフをしたほうが良い");
        var res = new TreeNode[this.children.Length];
        res[root] = new TreeNode(root, -1, 0, this.children[root].ToArray());

        var queue = new Queue<int>();
        foreach (var child in res[root].children)
        {
            res[child] = new TreeNode(child, root, 1, Array.Empty<int>());
            queue.Enqueue(child);
        }

        while (queue.Count > 0)
        {
            var from = queue.Dequeue();
            if (res[from].root == -1)
                res[from].children = this.children[from].ToArray();
            else
            {
                var children = new List<int>(this.children[from].Count);
                foreach (var c in this.children[from])
                    if (c != res[from].root)
                        children.Add(c);

                res[from].children = children.ToArray();
            }

            foreach (var child in res[from].children)
            {
                res[child] = new TreeNode(child, from, res[from].depth + 1, Array.Empty<int>());
                queue.Enqueue(child);
            }
        }

        return res;
    }

    public Node[] ToArray() =>
        Enumerable
        .Zip(roots, children, (r, c) => Tuple.Create(r, c))
        .Select((t, i) => new Node(i, t.Item1.ToArray(), t.Item2.ToArray()))
        .ToArray();
}
class TreeNode
{
    public TreeNode(int i, int root, int depth, int[] children)
    {
        this.index = i;
        this.root = root;
        this.children = children;
        this.depth = depth;
    }
    public readonly int index;
    public readonly int root;
    public readonly int depth;
    public int[] children;

    public override string ToString() => $"children: {string.Join(",", children)}";
    public override bool Equals(object obj)
    {
        if (obj is TreeNode)
            return this.Equals((TreeNode)obj);
        else
            return false;
    }
    public bool Equals(TreeNode other) => this.index == other.index;
    public override int GetHashCode() => this.index;
}
class Node
{
    public Node(int i, int[] roots, int[] children)
    {
        this.index = i;
        this.roots = roots;
        this.children = children;
    }
    public readonly int index;
    public readonly int[] roots;
    public readonly int[] children;

    public override string ToString() => $"children: {string.Join(",", children)}";
    public override bool Equals(object obj)
    {
        if (obj is Node)
            return this.Equals((Node)obj);
        else
            return false;
    }
    public bool Equals(Node other) => this.index == other.index;
    public override int GetHashCode() => this.index;
}


Measured memory_bytes: 197288