# https://www.acmicpc.net/problem/4766
# boj, 4766: 일반 화학 실험, python3
def solve(temps: list):
for x in range(len(temps)):
if temps[x+1] == 999:
break
print('%.2f' % (temps[x+1] - temps[x]))
if __name__ == '__main__':
temps = []
while True:
temp = float(input())
temps.append(temp)
if temp == 999: # 입력 온도가 999면 무한반복문 탈출
break
solve(temps)