# addmach3.py
# Written by Todd Wareham for CS 2500
"""
Implements interactive adding machine with these commands:

    "+ X"  : Add floating number X to sum
    "- X"  : Subtract floating number X from sum
    "="    : Print value of sum
    "stop" : Exit session

This version is implemented using the Decimal numeric datatype,
 functions, and a dictionary-based function lookup table..
"""

from decimal import Decimal

def add(num1, num2):
    return num1 + num2

def sub(num1, num2):
    return num1 - num2



op = {"+" : add, "-" : sub}
sum = Decimal("0.0")
while True:
    line = raw_input()
    if (line.split()[0] in ["+", "-"]):
        sum = op[line.split()[0]](sum, Decimal(line.split()[1]))
    elif (line.split()[0] == "="):
        print sum
    elif (line.split()[0] == "stop"):
        break