#include <bits/stdc++.h>
using namespace std;
const long long mod = (long long)1e9 + 7;
const long long inf = (long long)1e16;
const long double eps = 1e-12;
const long long N = (int)1e5 + 5;
const long long LOGN = 19;
const long double PI = 3.14159265358979323846;
inline long long mul(long long a, long long b, long long m = mod) {
  return (long long)(a * b) % m;
}
inline long long add(long long a, long long b, long long m = mod) {
  a += b;
  if (a >= m) a -= m;
  if (a < 0) a += m;
  return a;
}
inline long long power(long long a, long long b, long long m = mod) {
  if (b == 0) return 1;
  if (b == 1) return (a % m);
  long long x = power(a, b / 2, m);
  x = mul(x, x, m);
  if (b % 2) x = mul(x, a, m);
  return x;
}
bool check(string& k) {
  int l = 0, r = k.size() - 1;
  while (l < r) {
    if (k[l] != k[r]) {
      return false;
    }
    l++;
    r--;
  }
  return true;
}
bool poss(string& k) {
  map<char, int> mp;
  int num = 0;
  for (int i = 0; i < k.length(); i++) {
    if (mp.find(k[i]) == mp.end()) {
      mp[k[i]]++;
      num++;
    }
  }
  if (num == 1) return false;
  return true;
}
int rec(string& s) {
  int n = s.length();
  if (!poss(s)) return -1;
  if (!check(s)) return 0;
  string k;
  for (int i = 0; i < n / 2; i++) {
    k += s[i];
  }
  bool ok = check(k);
  if (!ok) {
    if (n & 1) return 2;
    return 1;
  }
  int ret = rec(k);
  if (ret == -2) {
    if (n & 1) return 2;
    return 1;
  }
  if (ret == -1) {
    if (n & 1) return -2;
    return -1;
  }
  return ret;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  if (0) {
    freopen("C:\\Users\\Dishant\\Desktop\\Collection-DEV c++\\input.txt", "r",
            stdin);
    freopen("C:\\Users\\Dishant\\Desktop\\Collection-DEV c++\\output.txt", "w",
            stdout);
  }
  string s;
  cin >> s;
  int n = s.length();
  int ans = rec(s);
  if (ans <= -1) {
    cout << "Impossible";
  } else
    cout << ans;
  return 0;
}
