兆数

给定数N ，任务是找到^第N^个兆数。

A Megagon number is a class of figurate numbers. It has a 1000000-sided polygon called Megagon. The N-th Megagon number count’s the 1000000 number of dots and all other dots are surrounding with a common sharing corner and make a pattern. The first few Megagonol numbers are 1, 1000000, 2999997, 5999992, 9999985, 14999976, … 
 

例子：

Input: N = 2 
Output: 1000000 
Explanation: 
The second Megagonol number is 1000000. 
Input: N = 3 
Output: 2999997 
 

方法：第N个百万像素数由以下公式给出：

• 侧多边形的第N个项= $\frac{((s-2)n^2 - (s-4)n)}{2}$
• 因此1000000个多边形的第N个项是

$Tn =\frac{((1000000-2)n^2 - (1000000-4)n)}{2} =\frac{(999998^2 - 999996)}{2}$

下面是上述方法的实现：

C++

// C++ implementation for the
// above approach
#include 
using namespace std;
 
// Function to find the
// nth Megagon Number
int MegagonNum(int n)
{
    return (999998 * n * n - 999996 * n) / 2;
}
 
// Driver Code
int main()
{
    int n = 3;
    cout << MegagonNum(n);
 
    return 0;
}

Java

// Java program for the above approach
class GFG{
 
// Function to find the
// nth Megagon Number
static int MegagonNum(int n)
{
    return (999998 * n * n - 999996 * n) / 2;
}
 
// Driver code
public static void main(String[] args)
{
    int n = 3;
     
    System.out.print(MegagonNum(n));
}
}
 
// This code is contributed by shubham

Python3

# Python3 implementation for the
# above approach
 
# Function to find the
# nth Megagon Number
def MegagonNum(n):
 
    return (999998 * n * n - 999996 * n) // 2;
 
# Driver Code
n = 3;
print(MegagonNum(n));
 
# This code is contributed by Code_Mech

C#

// C# program for the above approach
using System;
class GFG{
 
// Function to find the
// nth Megagon Number
static int MegagonNum(int n)
{
    return (999998 * n * n - 999996 * n) / 2;
}
 
// Driver code
public static void Main(String[] args)
{
    int n = 3;
     
    Console.Write(MegagonNum(n));
}
}
 
// This code is contributed by sapnasingh4991

Javascript

 
// Javascript implementation for the
// above approach
 
// Function to find the
// nth Megagon Number
function MegagonNum(n)
{
    return (999998 * n * n - 999996 * n) / 2;
}
 
// Driver Code
var n = 3;
document.write(MegagonNum(n));
 
 

输出：

2999997

参考： https ： //en.wikipedia.org/wiki/Megagon