from collections import deque

with open('data01.txt') as f:
	data = f.read().strip()


d = deque(data)
total = 0

'''
#part 1
for i in range(len(data)):
	if d[0] == d[1]:
		total += int(d[0])
	d.rotate()
'''

# part 2
half = len(data) // 2
for i in range(len(data)):
	if d[0] == d[half]:
		total += int(d[0])
	d.rotate()

print(total)