import math
import matplotlib.pyplot as plt
n=int(input("n = "))
x=[i for i in range(n+1)]
y=[]
y2=[math.pi/4 for i in range(n+1)]
a=0
for i in range(n+1):
  a=a+(-1)**i/(2*i+1)
  y.append(a)
plt.plot(x,y,'ob',markersize='2')
plt.plot(x,y2,'or:',markersize='2')
plt.grid()
plt.show()