Problem:
Score : 100 points

Problem Statement

Given is an integer r.

How many times is the area of a circle of radius r larger than the area of a circle of radius 1?

It can be proved that the answer is always an integer under the constraints given.

Constraints

1 \leq r \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

r

Output

Print the area of a circle of radius r, divided by the area of a circle of radius 1, as an integer.

Sample Input 1

2

Sample Output 1

4

The area of a circle of radius 2 is 4 times larger than the area of a circle of radius 1.

Note that output must be an integer - for example, 4.0 will not be accepted.

Sample Input 2

100

Sample Output 2

10000

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

using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using static System.Console;
using static System.Math;

class Program
{
    static void Main()
    {
        var N = int.Parse(ReadLine());
        WriteLine(N * N);
    }
}

public class NextPermutation
{
    int[] perm;
    public int Length => perm.Length;

    public NextPermutation(int N)
    {
        perm = new int[N];
        for (int i = 0; i < perm.Length; i++)
        {
            perm[i] = i;
        }
    }

    public NextPermutation(int[] init)
    {
        perm = init;
    }

    public int this[int i]
    {
        get
        {
            return perm[i];
        }
    }

    public bool Next()
    {
        var l = 0;
        for (int i = perm.Length - 2; i >= 0; i--)
        {
            if (perm[i] < perm[i + 1])
            {
                l = i;
                break;
            }
        }

        var v = perm[l];
        var r = 0;
        for (int i = perm.Length - 1; i >= 0; i--)
        {
            if (perm[i] > v)
            {
                r = i;
                break;
            }
        }

        if (l == 0 && r == 0) return false;
        Swap(ref perm[l++], ref perm[r]);
        Array.Reverse(perm, l, perm.Length - l);
        return true;
    }

    static void Swap<T>(ref T l, ref T r)
    {
        var t = l;
        l = r;
        r = t;
    }
}