A = input()
n = len(A)

def solve(l,r,m):
    # print(l,r,m)
    for x,y in zip(l,r):
        if x != y:
            return
    
    ans = l[::-1] + m + l
    print(ans)
    exit()
for i in range(n):
    l = A[:i][::-1]
    r = A[i+1:]
    # r = r[::-1]
    if len(l) >= len(r):
        solve(l,r,A[i])
    l = A[:i+1][::-1]
    if len(l) >= len(r):
        solve(l,r,"")