#include <bits/stdc++.h>
using namespace std;
int main()
{
    int a[20],b[20],c[20]={7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2},i,sum=0;
    char d[20]={'1','0','X','9','8','7','6','5','4','3','2'};
    for(i=0;i<17;i++)
    {
        cin>>a[i];
        sum+=a[i]*c[i];
    }
    sum%=11;
    cout<<d[sum]<<endl;
    return 0;
}
/**************************************************************
	Problem: 2028
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:28 ms
	Memory:2072 kb
****************************************************************/