import matplotlib.pyplot as plt
a = [0,1, 1,3, 3,9, 9, 12, 12, 18, 18,20, 20]
b = [100,100, 90,90, 80,80, 68,68, 54,54, 35,35, 15]
plt.plot(a, b)
plt.plot(a,b,"rD", markevery=2)
plt.xlabel('Follow-up time(months)')
plt.ylabel('Cummiliative Survival(%)')
plt.title('Kaplan-Meier Curve')