c,r=map(int,input().split())
tmc=c
tmc+=1
#分母and回数
bo=tmc*r

ls=[]
for i in range(c+1):
    for j in range(r):
        ls.append(i)

su=0
bos=1/bo

som=0
for i in ls:
    som+=bos*i

print(som)