#include <iostream>
using namespace std;
char a[11];
int main()
{
while(cin >> a)
{
int sum = 0;
int index = 0;
int i;
for(i = 0; i < 10; i++)
{
if(a[i] == '?')
index = i;
else if(a[i] == 'X')
sum += (10-i) * 10;
else
sum += (10-i) * (a[i] - '0');
}
for(i =0; i <= 10; i++)
{
if((sum + i *(10 - index))%11 == 0 )
break;
}
if(i == 10)
{
if(index != 9)
cout << "-1" << endl;
else
cout << "X" << endl;
}
else
cout << i << endl;
}
return 0;
}