#include <iostream>
#include <queue>
#include <stack>
#include <vector>
#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <string>
#include <cmath>
#include <complex>
#include <map>
using namespace std;

#define rep(i,n) for(int i=0;i<int(n);++i)
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define EPS 1e-8
#define F first
#define S second

static const double PI=6*asin(0.5);
typedef pair<double,double> P;
typedef complex<double> CP;
typedef long long ll;


int num[11];
char t;

int main(){
	while(cin>>t){
		num[0]=t-'0';
		rep(i,9){
			cin>>t;
			num[i+1]=t-'0';
		}
		rep(i,9){
			rep(j,9-i){
				num[j]=(num[j]+num[j+1])%10;
			}
		}
		cout<<num[0]<<endl;
	}
	return 0;
}