#include <iostream>
using namespace std;
int n;
int cifreImpare(int n)		
{				
    int s = 0, cn = n, p = 1;
    while (n > 0)		
    {
	    if (n % 2 == 0)		
	    {
	        s = n % 10 * p + s;	
	        p = p * 10;		
	    }
	    n = n / 10;		
    }
    if (s == 0 || s == cn)
	    return -1;
    return s;
}

int main()
{
    cin >> n;
    cout << cifreImpare(n);
    return 0;
}