a,b=map(int,input().split())
if b==1:
    S=a*(1+0.0325)
if b==2:
    S=a*0.0375*2+a
if 3<=b<=4:
    S=a*0.0425*b+a
if 5<=b:
    S=a*0.0475*b+a
print('%.1f'% S)
/**************************************************************
	Problem: 1341
	User: admin
	Language: Python
	Result: Accepted
	Time:234 ms
	Memory:34480 kb
****************************************************************/