def dfs(n, used):

    ans = 0
    for i in range(len(n)):
        if used[i]:
            continue
        for j in range(i + 1, len(n)):
            if used[j]:
                continue
            for k in range(j + 1, len(n)):
                if used[k]:
                    continue
                if n[i] != n[j] and n[j] == n[k]:
                    x = int(n[i] + n[j] + n[k])
                    used[i] = used[j] = used[k] = True
                    ans = max(ans, x + dfs(n, used))
                    used[i] = used[j] = used[k] = False
    return ans


def main():
    n = input()
    used = [False for _ in range(len(n))]
    print(dfs(n, used))

if __name__ == '__main__':
    main()