#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;

string s;
int c[10][10];

void solve(int num){
	if (num == 1)return;

	for (int i = 0; i < num - 1; i++){
		c[10 - num + 1][i] = (c[10 - num][i] + c[10 - num][i + 1]) % 10;
	}

	solve(num - 1);
}

int main(){
	while (cin >> s){
		REP(i, 10)c[0][i] = s[i] - '0';
		solve(10);
		cout << c[9][0] << endl;
	}
}