##斐波那契数列
A=[]
nterms =100
n1 = 0
n2 = 1
count = 2
if nterms>1:
    A.append(1)
    while count < nterms:
       nth = n1 + n2
       A.append(nth)
       n1 = n2
       n2 = nth
       count += 1

##判断素数函数
import math
def isprime1(x):
    if x==1:
        return False
    for i in range(2,int(math.sqrt(x)+1)):
        if x % i == 0:
            return False
    return True

##倒序输出字符
def reverse(x):
    o = 0
    while x:
        p = x % 10
        o = o * 10 + p
        x //= 10
    return o   

##求随机整数的均值
import random
A=range(0,101,1)
B=random.sample(A,k=10)
print(B)
C=random.randint(2, 6)
D=random.sample(B,k=C)
print(D)
average=sum(D)/len(D)
print(average)
##圆周率近似值
y=eval(input())
n=1
s=0
while n>0:
    if (1/(2*n-1)) >= y:
        s=(((-1)**(n-1))/(2*n-1))+s
        n=n+1
    else:
       break
pi=4*s
print("pi的近似值为:",pi)
##阶乘函数
def jiecheng(x):
    n=1
    if x==0:
        return 1
    elif x>0:
        for i in range(1,x+1):
            n=n*i
        return n
##组合数公式函数
def combine(m,n):
    return int(jiecheng(m)/(jiecheng(n)*jiecheng(m-n)))
##组合数求和函数
def combinesum(x):
    s=1
    if x==0:
        return 1
    elif x>0:
        for i in range(0,x):
            s=s+combine(x,i)
        return s
##构造杨辉三角形求和
def yanghuitriangle(n):
    s=0
    for i in range(0,n+1):
        s=s+combinesum(i)
    return s