A = list(input())
N = len(A)
flag1 = False
for i in range((N+1)//2,N):
    flag1 = True
    for j in range(i-1,-1,-1):
        if i+i-j-1>=N:break
        if A[j]!=A[i+i-j-1]:
            flag1 = False
            break
    if flag1:
        B = A[:i]
        ans1 = B+B[::-1]
        break
flag2 = False
for i in range(N//2,N):
    flag2 = True
    for j in range(i+1,N):
        if A[j]!=A[i-(j-i)]:
            flag2 = False
            break
    if flag2:
        B = A[:i]
        ans2 = B+[A[i]]+B[::-1]
        break
if flag1 and flag2:
    if len(ans1)<len(ans2):
        print(''.join(ans1))
    else:
        print(''.join(ans2))
elif flag1 and not flag2:
    print(''.join(ans1))
else:
    print(''.join(ans2))