s = input()

n = len(s)
res = ''
for i in range(n - 1):
    res += s[i]
    res += '$'
res += s[n - 1]
m = len(res)
mid = m // 2
for i in range(mid, m):
    l, r = i - 1, i + 1
    flag = True
    while l >= 0 and r < m:
        if res[l] != res[r]:
            flag = False
            break
        l -= 1
        r += 1
    if flag:
        l, r = i - 1, i + 1
        ans = s
        while l >= 0:
            if l % 2 == 0 and r >= m:
                ans += res[l]
            l -= 1
            r += 1
        print(ans)
        break