题解 | #牛牛的绩点#

n=0
s=0
a=[]
b=[]
l1=['A','B','C','D','F']
l2=[4.0,3.0,2.0,1.0,0.0]
l3=['1','2','3','4','5','6','7','8','9']
while True:
    m=input()
    if m in l1:
       e=m
       c=l1.index(e)
       a.append(l2[c])
    elif m in l3:
       e=int(m)
       b.append(e)
    else:
       break
for i in range(0,len(a)):
    n=n+a[i]*b[i]
s=sum(b)
print('%.2f'%(n/s))