G

from math import *

inp = input().split()
stack = []
s = ''

for i in inp:
    if i == '+':
        if len(stack) < 2:
            s = 'ERROR'
            break
        else:
            stack.append(stack.pop(-1) + stack.pop(-1))

    elif i == '-':
        if len(stack) < 2:
            s = 'ERROR'
            break
        else:
            stack.append(-stack.pop(-1) + stack.pop(-1))

    elif i == '*':
        if len(stack) < 2:
            s = 'ERROR'
            break
        else:
            stack.append(stack.pop(-1) * stack.pop(-1))

    elif i == '/':
        if len(stack) < 2:
            s = 'ERROR'
            break
        else:
            stack.append(1 / stack.pop(-1) * stack.pop(-1))

    elif i == 'abs':
        if len(stack) == 0:
            s = 'ERROR'
            break
        else:
            stack.append(abs(stack.pop(-1)))

    elif i == 'sin':
        if len(stack) == 0:
            s = 'ERROR'
            break
        else:
            stack.append(sin(stack.pop(-1)))

    elif i == 'cos':
        if len(stack) == 0:
            s = 'ERROR'
            break
        else:
            stack.append(cos(stack.pop(-1)))

    elif i == 'sqrt':
        if len(stack) == 0:
            s = 'ERROR'
            break
        else:
            stack.append(sqrt(stack.pop(-1)))

    else:
        stack.append(int(i))

    #print(stack)

if len(stack) != 1:
    s = 'ERROR'
if s != 'ERROR':
    s = '{0:.3f}'.format(stack[0])
print(s)