ошибка eoferror: eof when reading a line. в чем проблема

lst = []

while True:
    a = input()
    if a == '':
        break
    else:
        a = int(a)
        lst.append(a)

if len(lst) == 0:
    print(-1)
else:
    print(sum(lst) / len(lst))

ошибка

Traceback (most recent call last):
  File "/temp/executing/solution.py", line 4, in <module>
    a = int(input())
EOFError: EOF when reading a line
make: *** [run] Error 1