s = input()
ans = 0
d = {
"A+": 4.5,
"A": 4.0,
"B+": 3.5,
"B": 3.0,
"C+": 2.5,
"C": 2.0,
"D+": 1.5,
"D": 1.0,
"F": 0.0,
}
cnt = 0
for i in range(len(s)):
if s[i] == '+':
continue
z = s[i]
if i + 1 < len(s) and s[i + 1] == '+':
z += '+'
cnt += 1
ans += d[z]
print(ans / cnt)