A = list(input())
N = len(A)
if N==1:
    print(A[0])
elif A==[A[0]]*N:
    print("".join(A))
else:
    flag = True
    for i in range((N+1)//2,N):
        flag = True
        for j in range(i-1,-1,-1):
            if i+i-j-1>=N:break
            if A[j]!=A[i+i-j-1]:
                flag = False
                break
        if flag:
            B = A[:i]
            ans = B+B[::-1]
            break
    if flag:
        print("".join(ans))
    else:
        for i in range(N//2,N):
            flag = True
            for j in range(i+1,N):
                if A[j]!=A[i-(j-i)]:
                    flag = False
                    break
            if flag:
                B = A[:i]
                ans = B+[A[i]]+B[::-1]
                break
        print("".join(ans))