s = str(input())
s = list(s)
from collections import deque
s = deque(s)
ans = []
if len(s)%2 == 1:
    for i in range(len(s)):
        if i%2 == 0:
            ans.append(s.popleft())
        else:
            ans.append(s.pop())
else:
    for i in range(len(s)):
        if i%2 == 1:
            ans.append(s.popleft())
        else:
            ans.append(s.pop())
ans.reverse()
print(''.join(ans))