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#include<cstdio>
#include<iostream>

using namespace std;

int c;

int main()
{
	string str="秒";
	cout<<"请输入您的计算次数（越大越精准）：";
	cin>>c;
	cout<<"预计计算时间：";
	printf("%.5lf",0.00000002*c);
	cout<<"秒"<<endl;
	cout<<"正在计算中，请耐心等待！"<<endl ;  
	double a=3,b=1,d;
	for(int f=1;f<=c;f++)//无限循环！！！ 
	{ 
	    b = (b - 1 / a);
        a = (a + 2);
        b = (b + 1 / a);
        a = (a + 2);
        d=4*b;
	};
	cout<<"最后的π计算结果为：(默认保留50位小数)" ;
	printf("%.50lf\n",d);
	cout<<"本次计算结果仅供参考" ;
	return 0;
}