a = input().split()
x = int(a[0])
n = int(a[1])
t = 1
z=2
ssum=0
for i in range(1,n+1):
y=x*t
t+=1
z+=1
h=z
while z!=0:
z-=1
mu=hz
mu2=mu/h
mu3=mu2*h
ssum+=y/mu3
print(ssum)
#ZeroDivisionError: float division by zero