Problem:
Score : 200 points

Problem Statement

Takahashi loves numbers divisible by 2.

You are given a positive integer N. Among the integers between 1 and N (inclusive), find the one that can be divisible by 2 for the most number of times. The solution is always unique.

Here, the number of times an integer can be divisible by 2, is how many times the integer can be divided by 2 without remainder.

For example,

6 can be divided by 2 once: 6 -> 3.

8 can be divided by 2 three times: 8 -> 4 -> 2 -> 1.

3 can be divided by 2 zero times.

Constraints

1 ≤ N ≤ 100

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

7

Sample Output 1

4

4 can be divided by 2 twice, which is the most number of times among 1, 2, ..., 7.

Sample Input 2

32

Sample Output 2

32

Sample Input 3

1

Sample Output 3

1

Sample Input 4

100

Sample Output 4

64

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Library;
using static Library.Input;

namespace AtCoderTemplate {
    class ProgramB {
        static void Main () {  
            int N = NextInt;
            int ans = 1;
            while(ans * 2 <= N) ans *= 2;
            System.Console.WriteLine(ans);
        }
    }
}

namespace Library {
    class Input {
        static IEnumerator<string> enumerator = new string[] { }.AsEnumerable ().GetEnumerator ();

        public static string Line => Console.ReadLine ();

        public static string[] StrArr => Line.Split (' ');

        public static int NextInt => int.Parse (NextWord ());

        public static long NextLong => long.Parse (NextWord ());

        public static List<int> IntList => StrArr.Select (int.Parse).ToList ();

        public static List<long> LongList => StrArr.Select (long.Parse).ToList ();

        public static IEnumerable<long[]> TakeLine (int N) {
            return Enumerable.Repeat (0, N).Select (_ => Console.ReadLine ().Split (' ').Select (long.Parse).ToArray ());
        }

        public static string NextWord () {
            while (!enumerator.MoveNext ()) {
                enumerator = StrArr.AsEnumerable ().GetEnumerator ();
            }
            return enumerator.Current;
        }
    }
}

namespace Library {
    
    class Modular {
        public const int mod = 1000000007;
        public readonly long value;
        public Modular (long value) { this.value = value; }
        public static implicit operator Modular (long a) {
            var m = a % mod;
            return new Modular ((m < 0) ? m + mod : m);
        }
        public static Modular operator + (Modular a, Modular b) {
            return a.value + b.value;
        }
        public static Modular operator - (Modular a, Modular b) {
            return a.value - b.value;
        }
        public static Modular operator * (Modular a, Modular b) {
            return a.value * b.value;
        }
        public static Modular Pow (Modular a, int n) {
            switch (n) {
                case 0:
                    return 1;
                case 1:
                    return a;
                default:
                    var p = Pow (a, n / 2);
                    return p * p * Pow (a, n % 2);
            }
        }
        public static Modular operator / (Modular a, Modular b) {
            return a * Pow (b, mod - 2);
        }
        private static readonly List<int> facs = new List<int> { 1 };
        private static Modular Fac (int n) {
            for (int i = facs.Count; i <= n; ++i) {
                facs.Add ((int) (Math.BigMul (facs.Last (), i) % mod));
            }
            return facs[n];
        }
        public static Modular Ncr (int n, int r) {
            return (n < r) ? 0 :
                (n == r) ? 1 :
                Fac (n) / (Fac (r) * Fac (n - r));
        }
        public static explicit operator int (Modular a) {
            return (int) a.value;
        }
    }

}
namespace Library {
    class MyMath {
        public static long Gcd (long a, long b) {
            return b == 0 ? a : Gcd (b, a % b);
        }

        public static long Sqrt (long n) {
            if (n < 0) return 0;
            long a = 0, tmp = 0, b = 0;
            for (int i = 62; i >= 0; i -= 2) {
                tmp = (b << 1) + 1 <= (n >> i) ? 1 : 0;
                a = a << 1 | tmp;
                n -= (((b << 1) + 1) * tmp) << i;
                b = (b << 1) + tmp + tmp;
            }
            return a;
        }

        public static long Nck (int n, int k) {
            if (k == 0) return 1;
            if (n == 0) return 0;
            return n * Nck (n - 1, k - 1) / k;
        }
    }
}

namespace Library {
        public class PriorityQueue<T> {

        readonly List<T> _heap = new List<T> ();
        readonly Comparison<T> _comparison;

        public PriorityQueue (Comparison<T> comparison) {
            _comparison = comparison;
        }

        public PriorityQueue () : this (Comparer<T>.Default.Compare) { }

        public PriorityQueue (IComparer<T> comparer) : this (comparer.Compare) { }

        public void Enqueue (T item) {
            _heap.Add (item);

            int childID = _heap.Count - 1;
            int parentID = (childID - 1) / 2;

            while (childID > 0 && _comparison (_heap[parentID], _heap[childID]) > 0) {
                Swap (parentID, childID);
                childID = parentID;
                parentID = (parentID - 1) / 2;
            }
        }

        public T Dequeue () {
            var first = _heap.First ();
            _heap[0] = _heap.Last ();
            _heap.RemoveAt (_heap.Count - 1);

            int parentID = 0;
            int childID = parentID * 2 + 2;
            if (childID >= _heap.Count || _comparison (_heap[childID], _heap[childID - 1]) > 0) childID--;

            while (childID < _heap.Count && _comparison (_heap[parentID], _heap[childID]) > 0) {
                Swap (parentID, childID);
                parentID = childID;
                childID = parentID * 2 + 2;
                if (childID >= _heap.Count || _comparison (_heap[childID], _heap[childID - 1]) > 0) childID--;
            }

            return first;
        }

        void Swap (int parent, int child) {
            var tmp = _heap[parent];
            _heap[parent] = _heap[child];
            _heap[child] = tmp;
        }

        public T Peek () { return _heap[0]; }
        public int Count => _heap.Count;
        public bool Any () { return _heap.Any (); }
        public List<T> Data => _heap;
    }
}

namespace Library {
    
    public class UnionFind {
        public int[] Parents { get; set; }
        public UnionFind (int size) {
            Parents = Enumerable.Repeat (-1, size).ToArray ();
        }

        public int Find (int num) {
            if (Parents[num] < 0) return num;

            Parents[num] = Find (Parents[num]);
            return Parents[num];
        }

        public int Size (int num) {
            return -Parents[Find (num)];
        }

        public bool Same (int a, int b) {
            return Find (a) == Find (b);
        }

        public void Unite (int a, int b) {
            int x = Find (a), y = Find (b);

            if (Size (x) > Size (y)) {
                Parents[x] += Parents[y];
                Parents[y] = x;
            } else {
                Parents[y] += Parents[x];
                Parents[x] = y;
            }
        }
    }
}