#include <iostream>
#include <algorithm>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = unsigned;
using u64 = unsigned long long;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

int main() {
    vector<int> c{1, 9, 6, 4, 6, 6, 4, 6, 9, 1};
    string s;
    while(cin >> s){
        int ans = 0;
        for (int i = 0; i < 10; ++i) ans += c[i]*(s[i]-'0');
        cout << ans%10 << "\n";
    }
    return 0;
}
