import java.util.*; import java.io.*; public class Main { static final int INF = 1<<30; static final long INFL = 1L<<60; static final int MOD = 1000000007; static final int MOD2 = 998244353; static List> g; public static void main(String[] args) { FastScanner fs = new FastScanner(); PrintWriter pw = new PrintWriter(System.out); char[] s = fs.nextChars(); int n = s.length; boolean ok = true; Set set = new HashSet<>(); for(int i = 0; i < n; i++){ if(s[i] != s[n-1-i]) ok = false; set.add(s[i]); } if(!ok) pw.println(n); else { if(set.size() == 1){ if(n%2 == 0) pw.println(0); else pw.println(-1); } else if(n == 3) pw.println(-1); else pw.println(n-2); } pw.close(); } } class FastScanner { private InputStream in = System.in; private byte[] buffer = new byte[1024]; private int length = 0, p = 0; private boolean hasNextByte() { if (p < length) return true; else{ p = 0; try{ length = in.read(buffer); }catch(Exception e){ e.printStackTrace(); } if(length == 0) return false; } return true; } private int readByte() { if (hasNextByte() == true) return buffer[p++]; return -1; } private static boolean isPrintable(int n) { return 33 <= n && n <= 126; } private void skip() { while (hasNextByte() && !isPrintable(buffer[p])) p++; } public boolean hasNext() { skip(); return hasNextByte(); } public String next() { if(!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int temp = readByte(); while (isPrintable(temp)) { sb.appendCodePoint(temp); temp = readByte(); } return sb.toString(); } public int nextInt() { return Math.toIntExact(nextLong()); } public int[] nextInts(int n) { int[] ar = new int[n]; for (int i = 0; i < n; i++) ar[i] = nextInt(); return ar; } public long[] nextLongs(int n) { long[] ar = new long[n]; for (int i = 0; i < n; i++) ar[i] = nextLong(); return ar; } public long nextLong() { if(!hasNext()) throw new NoSuchElementException(); boolean minus = false; int temp = readByte(); if (temp == '-') { minus = true; temp = readByte(); } if (temp < '0' || '9' < temp) throw new NumberFormatException(); long n = 0; while (isPrintable(temp)) { if ('0' <= temp && temp <= '9') { n *= 10; n += temp - '0'; } temp = readByte(); } return minus ? -n : n; } public char[] nextChars() { String s = next(); return s.toCharArray(); } public char[][] nextCharMat(int h, int w) { char[][] ar = new char[h][w]; for(int i = 0; i < h; i++){ String s = next(); for(int j = 0; j < w; j++){ ar[i][j] = s.charAt(j); } } return ar; } }