# Topic : Implementation _ 과제 안 내신분?
#
# Python 3 : 72ms

students = [0]*31
students[0] = 1

for _ in range(28):
  n = int(input())

  students[n] = 1

# print(students)

for i in range(1,31):
  if students[i] == 0:
    print(i)