text: //
  //  AOJ0062.cpp
  //  
  //
  //  Created by knuu on 2014/06/18.
  //
  //
  
  #include <iostream>
  
  using namespace std;
  
  int main()
  {
  	int sum,pascal[10]={1,9,36,84,126,126,84,36,9,1};
  	double t;
  	char input[11];
  	while (cin>>input) {
  		sum=0;
  		for (int i=0; i<10; i++) sum+=(input[i]-'0')*pascal[i];
  		cout<<sum%10<<endl;
  	}
  }
  