import sys a = [] data_flag = 0 score = 0 timer = 0 score_tycle = {"A" :4.0,"B": 3.0,"C": 2.0,"D": 1.0,"F": 0} for line in sys.stdin: a +=line.split() for x in a: if x == "False": break else: if data_flag == 0: if x in score_tycle: tem = float(score_tycle[x]) data_flag = 1 else: try: data_flag = 0 tem = tem*float(x) timer =float(x) + timer score = tem+score except ValueError: continue print("%0.2f"%(score/timer))