using System; using System.Collections; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Linq; using System.Numerics; using System.Runtime.CompilerServices; using System.Text; using static System.Math; using static Extensions; using static MathExtensions; public static class Program { public static void Solve() { var t = I; var x = Repeat(t, () => I).ToArray(); if (Abs(x[0]) != 1) { Console.WriteLine("F"); Exit(0); } Repeat(t - 1, i => { if (Abs(x[i] - x[i + 1]) != 1) { Console.WriteLine("F"); Exit(0); } }); Console.WriteLine("T"); } #region Scanners static Scanner _scanner; static char C => _scanner.NextChar(); static string S => _scanner.NextString(); static int I => _scanner.NextInt(); static long L => _scanner.NextLong(); static BigInteger B => _scanner.NextBigInteger(); static double D => _scanner.NextDouble(); static decimal M => _scanner.NextDecimal(); #endregion public static void Main() { var sw = new StreamWriter(Console.OpenStandardOutput()); sw.NewLine = "\n"; #if DEBUG sw.AutoFlush = true; #else sw.AutoFlush = false; #endif Console.SetOut(sw); _scanner = new Scanner(Console.OpenStandardInput()); Solve(); Console.Out.Flush(); } } public static partial class Extensions { } #region Library public class Scanner { private readonly Stream _stream; private const int _bufferSize = 1024; private readonly byte[] _buf = new byte[_bufferSize]; private int _len, _ptr; public Scanner(Stream stream) { _stream = stream; } public byte ReadByte() { if (_ptr >= _len) { _len = _stream.Read(_buf, 0, _bufferSize); _ptr = 0; } return _buf[_ptr++]; } public char ReadChar() => (char)ReadByte(); public string ReadLine() { var r = new StringBuilder(); if (_ptr == 0) r.Append(ReadChar()); for (; _ptr < _len; _ptr++) r.Append((char)_buf[_ptr]); return r.ToString(); } public char NextChar() => char.Parse(NextString()); public string NextString() { var r = new StringBuilder(); var b = ReadChar(); while (b != ' ' && b != '\n') { r.Append(b); b = ReadChar(); } return r.ToString(); } public int NextInt() => (int)NextLong(); public long NextLong() { var r = 0L; var b = ReadByte(); var n = b == '-'; if (n) b = ReadByte(); while (b != ' ' && b != '\n') { r = r * 10 + b - '0'; b = ReadByte(); } return n ? -r : r; } public BigInteger NextBigInteger() { var r = new BigInteger(); var b = ReadByte(); var n = b == '-'; if (n) b = ReadByte(); while (b != ' ' && b != '\n') { r = r * 10 + b - '0'; b = ReadByte(); } return n ? -r : r; } public double NextDouble() { var i = 0L; var b = ReadByte(); var n = b == '-'; if (n) b = ReadByte(); while (b != '.' && b != ' ' && b != '\n') { i = i * 10 + b - '0'; b = ReadByte(); } if (b != '.') return n ? -i : i; b = ReadByte(); var f = 0L; var p = 0; while (b != ' ' && b != '\n') { f = f * 10 + b - '0'; b = ReadByte(); p++; } var r = i + (double)f / MathExtensions.Pow(10, p); return n ? -r : r; } public decimal NextDecimal() => decimal.Parse(NextString()); public T Next(Converter parser) => parser(NextString()); } [DebuggerStepThrough] public static partial class Extensions { [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Assert(bool condition) { if (!condition) throw new Exception("Assertion failed"); } public static string AsString(this IEnumerable source) => new string(source.ToArray()); public static void Exit(int exitCode) { Console.Out.Flush(); Environment.Exit(exitCode); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void ForEach(this IEnumerable source, Action action) { foreach (var item in source) action(item); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void ForEach(this IEnumerable source, Func func) { foreach (var item in source) func(item); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void ForEach(this IEnumerable source, Action action) { var i = 0; foreach (var item in source) action(item, i++); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void ForEach(this IEnumerable source, Func func) { var i = 0; foreach (var item in source) func(item, i++); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static T Iterate(int count, T seed, Func func) { var r = seed; for (var i = 0; i < count; i++) r = func(r); return r; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Repeat(int count, Action action) { for (var i = 0; i < count; i++) action(); } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static void Repeat(int count, Action action) { for (var i = 0; i < count; i++) action(i); } public static IEnumerable Repeat(Func func) { for (var i = 0; ; i++) yield return func(); } public static IEnumerable Repeat(int count, Func func) { for (var i = 0; i < count; i++) yield return func(); } public static IEnumerable Repeat(Func func) { for (var i = 0; ; i++) yield return func(i); } public static IEnumerable Repeat(int count, Func func) { for (var i = 0; i < count; i++) yield return func(i); } public static void Swap(ref T x, ref T y) { var tmp = x; x = y; y = tmp; } public static (T1[], T2[]) Unzip(this ICollection<(T1, T2)> source) { var ts1 = new T1[source.Count]; var ts2 = new T2[source.Count]; var i = 0; foreach (var (t1, t2) in source) { ts1[i] = t1; ts2[i] = t2; i++; } return (ts1, ts2); } public static (T1[], T2[], T3[]) Unzip(this ICollection<(T1, T2, T3)> source) { var ts1 = new T1[source.Count]; var ts2 = new T2[source.Count]; var ts3 = new T3[source.Count]; var i = 0; foreach (var (t1, t2, t3) in source) { ts1[i] = t1; ts2[i] = t2; ts3[i] = t3; i++; } return (ts1, ts2, ts3); } public static (T1[], T2[], T3[], T4[]) Unzip(this ICollection<(T1, T2, T3, T4)> source) { var ts1 = new T1[source.Count]; var ts2 = new T2[source.Count]; var ts3 = new T3[source.Count]; var ts4 = new T4[source.Count]; var i = 0; foreach (var (t1, t2, t3, t4) in source) { ts1[i] = t1; ts2[i] = t2; ts3[i] = t3; ts4[i] = t4; i++; } return (ts1, ts2, ts3, ts4); } public static IEnumerable Zip(this IEnumerable first, IEnumerable second, IEnumerable thrid, Func resultSelector) { using (var e1 = first.GetEnumerator()) using (var e2 = second.GetEnumerator()) using (var e3 = thrid.GetEnumerator()) { while (e1.MoveNext() && e2.MoveNext() && e3.MoveNext()) yield return resultSelector(e1.Current, e2.Current, e3.Current); } } public static IEnumerable Zip(this IEnumerable first, IEnumerable second, IEnumerable thrid, IEnumerable fourth, Func resultSelector) { using (var e1 = first.GetEnumerator()) using (var e2 = second.GetEnumerator()) using (var e3 = thrid.GetEnumerator()) using (var e4 = fourth.GetEnumerator()) { while (e1.MoveNext() && e2.MoveNext() && e3.MoveNext() && e4.MoveNext()) yield return resultSelector(e1.Current, e2.Current, e3.Current, e4.Current); } } } [DebuggerStepThrough] public static class MathExtensions { public static int Gcd(int left, int right) { int r; while ((r = left % right) != 0) { left = right; right = r; } return right; } public static long Gcd(long left, long right) { long r; while ((r = left % right) != 0L) { left = right; right = r; } return right; } public static BigInteger Gcd(BigInteger left, BigInteger right) => BigInteger.GreatestCommonDivisor(left, right); public static int HighestOneBit(int x) { x |= x >> 01; x |= x >> 02; x |= x >> 04; x |= x >> 08; x |= x >> 16; return x - (x >> 1); } public static long HighestOneBit(long x) { x |= x >> 01; x |= x >> 02; x |= x >> 04; x |= x >> 08; x |= x >> 16; x |= x >> 32; return x - (x >> 1); } public static int Lcm(int left, int right) => left / Gcd(left, right) * right; public static long Lcm(long left, long right) => left / Gcd(left, right) * right; public static BigInteger Lcm(BigInteger left, BigInteger right) => left / Gcd(left, right) * right; public static int Pow(int value, int exponent) { var r = 1; while (exponent > 0) { if ((exponent & 1) == 1) r *= value; value *= value; exponent >>= 1; } return r; } public static long Pow(long value, int exponent) { var r = 1L; while (exponent > 0) { if ((exponent & 1) == 1) r *= value; value *= value; exponent >>= 1; } return r; } public static long Fact(int value) { var r = 1L; for (var i = 2; i <= value; i++) r *= i; return r; } } #endregion