using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ProgrammingContest { class MainClass : IDisposable { Scanner sc; Writer wr; string backPath = ".."; char dirSep = System.IO.Path.DirectorySeparatorChar; string inFilePath = null; string outFilePath = null; public MainClass() { this.inFilePath = this.backPath + this.dirSep + this.backPath + this.dirSep + "in.txt"; this.outFilePath = this.backPath + this.dirSep + this.backPath + this.dirSep + "out.txt"; } static void Main(string[] args) { using (var mainClass = new MainClass()) { //mainClass.MakeTestCase(); mainClass.Solve(); } } public void Dispose() { if (this.sc != null) { this.sc.Dispose(); } if (this.wr != null) { this.wr.Dispose(); } } void MakeTestCase() { Random rand = new Random(); this.wr = new Writer(inFilePath); } void Solve() { this.wr = new Writer(this.isReactive); //this.wr = new Writer(this.outFilePath); #if DEBUG if (!this.isReactive) this.sc = new Scanner(this.inFilePath); else this.sc = new Scanner(); #else this.sc = new Scanner(); #endif long n = sc.NextLong; System.Numerics.BigInteger bi = System.Numerics.BigInteger.Zero; long high = n, low = 0; while (high - low > 10) { long mid1 = (high + (low << 1)) / 3; long mid2 = ((high << 1) + low) / 3; if (Calc(mid1, n - mid1) <= Calc(mid2, n - mid2)) { low = mid1; } else { high = mid2; } } System.Numerics.BigInteger ans = System.Numerics.BigInteger.Zero; for (long i = Math.Max(0, low - 100); i <= Math.Min(n, high + 100); i++) { var buf = Calc(i, n - i); if (ans < buf) ans = buf; } wr.WriteLine(ans % MOD); } System.Numerics.BigInteger Calc(long x, long y) { return new System.Numerics.BigInteger(y) * (x + 1) + x; } const int MOD = (int) 1e6 + 7; bool isReactive = false; // TODO: reactive check !! } class Writer : IDisposable { private System.IO.TextWriter writer; private StringBuilder sb; private bool isReactive; public Writer(string path) : this(new System.IO.StreamWriter(path)) { } public Writer(bool isReactive) : this(null, isReactive) { } public Writer(System.IO.TextWriter writer = null, bool isReactive = false) { this.writer = (writer ?? Console.Out); this.isReactive = isReactive; if (!this.isReactive) { this.sb = new StringBuilder(); } } public void Dispose() { if (!this.isReactive) this.writer.Write(sb.ToString()); if (!this.writer.Equals(Console.Out)) this.writer.Dispose(); } public void Write(object val) { if (this.isReactive) { this.writer.Write(val.ToString()); this.writer.Flush(); } else this.sb.Append(val.ToString()); } public void Write(string format, params object[] vals) { if (this.isReactive) { this.writer.Write(format, vals); this.writer.Flush(); } else this.sb.AppendFormat(format, vals); } public void WriteLine(object val) { this.Write(val.ToString() + System.Environment.NewLine); } public void WriteLine(string format, params object[] vals) { this.Write(format + System.Environment.NewLine, vals); } } class Scanner : IDisposable { private Queue buffer; private char[] sep; private System.IO.TextReader reader; public Scanner(string path) : this(new System.IO.StreamReader(path)) { } public Scanner(System.IO.TextReader reader = null) { this.buffer = new Queue(); this.sep = new char[] { ' ' }; this.reader = (reader ?? Console.In); } private void CheckBuffer() { if (this.buffer.Count == 0) { string str = string.Empty; while (string.IsNullOrEmpty(str)) { str = this.reader.ReadLine(); } str.Split(this.sep).ToList() .ForEach(el => this.buffer.Enqueue(el)); } } public void Dispose() { if (!this.reader.Equals(Console.In)) this.reader.Dispose(); } public string Next { get { this.CheckBuffer(); return this.buffer.Dequeue(); } } public int NextInt { get { return int.Parse(this.Next); } } public double NextDouble { get { return double.Parse(this.Next); } } public long NextLong { get { return long.Parse(this.Next); } } public bool IsEnd { get { this.CheckBuffer(); return this.buffer.Count == 0; } } } }