#include <iostream>
using namespace std;
int Polynomial(double x,int n);
int main ()
{
	
	int n;
	double x;
	//输入
	cout<<"请输入一个实数：";
	cin>>x;
	cout<<"请输入求n阶勒让德多项式的n值：";
	cin>>n;

	cout<<"该n阶勒让德多项式的值为："<<Polynomial(x,n)<<endl;
		
	return 0;
}

int Polynomial(double x,int n)//求n阶勒让德多项式的值的函数
{
	double p;
	if(n==0)
	{
		p=1;
	}
	else if(n==1) 
	{
		p=x;
	}
	else
	{
		p=((2*n-1)*x*Polynomial(x,n-1)-(n-1)*Polynomial(x,n-2))/n;
	}
	
	return p;
}