# -*- coding: utf-8 -*-
from __future__ import division

####################导入时间模块
import time
###############计算当前时间
time1=time.time()
################算法根据马青公式计算圆周率####################

#number = int(input('请输入想要计算到小数点后的位数n:'))
number = 10000*1000 # 计算一千万
# 多计算10位，防止尾数取舍的影响
number1 = number+10

# 算到小数点后number1位
b = 10**number1

# 求含4/5的首项
x1 = b*4//5
# 求含1/239的首项
x2 = b// -239

# 求第一大项
he = x1+x2
#设置下面循环的终点，即共计算n项
number *= 2

#循环初值=3，末值2n,步长=2
for i in range(3,number,2):
    # 求每个含1/5的项及符号
    x1 //= -25
    # 求每个含1/239的项及符号
    x2 //= -57121
    # 求两项之和
    x = (x1+x2) // i
    # 求总和
    he += x

# 求出π
pai = he*4
#舍掉后十位
pai //= 10**10

############ 输出圆周率π的值
paistring=str(pai)
result=paistring[0]+str('.')+paistring[1:len(paistring)]
print(result)
with open(".pi.result","w+",encoding="utf-8") as f:
    f.write(str(result))
time2=time.time()
print(u'总共耗时：' + str(time2 - time1) + 's')

with open(".pi.result","a+",encoding="utf-8") as f:
    f.write("\n")
    f.write(u'总共耗时：' + str(time2 - time1) + 's')