"""
[10408: The return of the King](https://www.acmicpc.net/problem/10408)
Tier: ??
Category: ??
"""
def solution(s):
l = []
i = 0
while i < len(s):
if int(s[i]) > 1:
l.append(int(s[i]))
else:
if i + 1 < len(s) and s[i + 1] == '0':
l.append(10)
i += 1
else:
l.append(1)
i += 1
return sum(l) / len(l)
if __name__ == '__main__':
print("%.2f" % solution(input()))