#include <bits/stdc++.h>
using namespace std;
string A;
bool isPalindrome(int left, int right) {
  while (left < right) {
    if (A[left] != A[right]) return false;
    left++, right--;
  }
  return true;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> A;
  int N = A.size();
  int bonus = 0;
  int ret = 0;
  if (N % 2 == 1) bonus = 1;
  N /= 2;
  while (N > 0) {
    if (isPalindrome(0, N - 1)) {
      if (N % 2 == 1) {
        N--;
        bonus = 1;
      } else
        N /= 2;
    } else {
      ret = 1 + bonus;
      break;
    }
  }
  if (ret == 0)
    cout << "Impossible";
  else
    cout << ret;
  return 0;
}
