https://www.acmicpc.net/problem/4766
# 일반 화학 실험
import sys
input = sys.stdin.readline # 시간 단축
ondo = []
while True:
temperature = float(input())
ondo.append(temperature)
if temperature == 999:
break
i = 0
while True:
if ondo[i+1] == 999 : break
print("%.2f" %(ondo[i+1]-ondo[i]))
i+=1