#include <functional>
#include <algorithm>
#include <iostream>
#include <numeric>
#include <iomanip>
#include <utility>
#include <cstdlib>
#include <sstream>
#include <bitset>
#include <vector>
#include <cstdio>
#include <ctime>
#include <queue>
#include <deque>
#include <cmath>
#include <stack>
#include <list>
#include <map>
#include <set>

using namespace std;

typedef vector<int> vi;
typedef pair<int,int> pii;
typedef long long ll;

#define dump(x)  cerr << #x << " = " << (x) << endl
#define rep(i,n) for(int i=0;i<(n);i++)
#define all(a)  (a).begin(),(a).end()
#define pb push_back


int main(){
  string s;
  cin>>s;
  int c=0;
  string a;
  rep(i,(int)s.size()){
    if(s[i]=='Z' || s[i]=='A')a+=s[i];
  }
  string ans;
  rep(i,(int)a.size()-1){
    if(a[i]=='A' && a[i+1]=='Z'){
      ans+="AZ";
      c++;
    }
  }
      
  if(c==0)cout<<"-1"<<endl;
  else cout<<ans<<endl;
  
  return 0;
}