n = int(input())
s = input()
stack = []
L = [int(input()) for i in range(n)]
for i in s:
if 'A' <= i <='Z':
stack.append(L[ord(i)-65])
else:
a = stack.pop()
b = stack.pop()
if i == '+':
stack.append(a+b)
elif i == '-':
stack.append(b-a)
elif i == '/':
stack.append(b/a)
elif i == '*':
stack.append(a*b)
print("%.2f" % (stack[0]))