#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <utility>
#include <functional>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <deque>
#include <ctime>
 
using namespace std;
 
#define rep(i,n) REP(i,0,n)
#define REP(i,s,e) for(int i=(s); i<(int)(e); i++)
#define pb push_back
#define mp make_pair
#define all(r) r.begin(),r.end()
#define fi first
#define se second
#define println(X) cout<<X<<endl;
#define DBG(X) cout<<#X<<" : "<<X<<endl;
 
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vii;
typedef vector<ll> vl;
typedef vector<vl> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

const int INF = 1e9;
const ll MOD = 1e9 + 7;
double EPS = 1e-3;

int dx[]={-1,0,1,0};
int dy[]={0,-1,0,1};

int main(){
	string s;
	cin>>s;
	int l = 0;
	for(int i = 0; i < s.size(); i++){
		if(l%2==0 && s[i]=='A') l++;
		else if(l%2==1 && s[i]=='Z') l++;
	}
	string ans;
	rep(i, l/2) ans+="AZ";
	if(ans.size()==0) {
		cout<<-1<<endl; 
		return 0;
	}
	cout<<ans<<endl;
}