#include<iostream.h>
#include<iomanip.h>
#include<time.h>
const unsigned long maxshort=65536L;
const unsigned long multiplier=1194211693L;
const unsigned long adder=12345;

class RandomNumber
{
private:
	unsigned long randSeed;  //當前種子
public:
	RandomNumber(unsigned long s=0);  //構(gòu)造函數(shù)
	unsigned short Random(unsigned long n);  //產(chǎn)生0到n-1之間的隨機整數(shù)
	double fRandom(void);  //產(chǎn)生[0，1]的隨機實數(shù)
};

RandomNumber::RandomNumber(unsigned long s)
{
	if (s==0)
		randSeed=time(0);  //用系統(tǒng)時間產(chǎn)生種子
	else
		randSeed=s;  //用戶提供種子
}
unsigned short RandomNumber::Random(unsigned long n)
{
	randSeed=multiplier*randSeed+adder;
	return (unsigned short)((randSeed>>16)%n);
}

double RandomNumber::fRandom(void)
{
	return Random(maxshort)/double(maxshort);
}
double Darts(int n)  //計算圓周率值
{
	static RandomNumber dart;
	int k=0;
	for(int i=1;i<=n;i++)
	{
		double x=dart.fRandom();
		double y=dart.fRandom();
		if((x*x+y*y)<1) k++;
	}
	return 4*k/double(n);
}
void main(void)
{
unsigned long n;
cout<<"n=";
cin>>n;
cout<<Darts(n)<<endl;
}