import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val s = nextLine()
    val t = s.reversed()
    if (s != t) {
        println(s.length)
    } else if (s.toCharArray().distinct().count() > 1) {
        println(s.length - 2)
    } else if (s.length % 2 == 0) {
        println(0)
    } else {
        println(-1)
    }
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()
fun nextDouble() = next().toDouble()
// endregion