#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using ll = long long;
using lint = long long;
typedef vector<long long> vint;
typedef pair<long long, long long> pint;
#define INF INT32_MAX / 2
#define INF64 INT64_MAX / 2
#define EPS 0.001
#define EPS14  1.0E-14
#define REP(i, n) for (ll i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define ALL(f,c,...) (([&](decltype((c)) cccc) { return (f)(std::begin(cccc), std::end(cccc), ## __VA_ARGS__); })(c))
#define c(n) cout<<n<<endl;
#define cf(n) cout<<fixed<<setprecision(15)<<n<<endl;
template <class T>inline bool chmin(T&a,T b) {if(a>b){a=b;return true;}return false;}
template <class T>inline bool chmax(T&a,T b) {if(a<b){a=b;return true;}return false;}
template<class T>inline T sum(T n){return n*(n+1)/2;}
map<ll,ll> prime_fac(ll A) {map<ll,ll>mp;for(ll i=2;i*i<=A;i++){while(A%i== 0){mp[i]++;A/=i;}}if(A!=1){mp[A]=1;}return mp;}
bool is_prime(ll N){if(N<=1)return false;for(ll i=2;i*i<=N;i++){if(N%i==0) return false;}return true;}
template<class T>inline T myceil(T a,T b){return (a+(b-1))/b;}
ll pw(ll x, ll n){ll ret=1;while(n>0){if(n&1){ret*=x;}x *= x;n >>= 1;}return ret;}
bool is_product_overflow(long long a,long long b) {long prod=a*b;return (prod/b!=a);}

int main() {
    ll p, q, r, K;
    cin >> p >> q >> r >> K;

    map<vector<ll>, ll> mp;
    vector<ll> roop = {p%10, q%10, r%10};
    ll cnt = 0;
    ll j = 0;
    REP (i, 15000) {
        roop.push_back({(roop[i] + roop[i + 1] + roop[i + 2]) % 10});
        vector<ll> vec = {roop[i]%10, roop[i + 1]%10, roop[i + 2]%10};
        if (mp.count(vec)) {
            cnt = i + 4 - mp[vec];
            j = mp[vec]-1;
            break;
        }

        mp[vec] = i + 4;
    }

    if (K <= roop.size()) c(roop[K-1])
    else {
        K -= j + 1;
        K %= cnt;
        c(roop[j + K])
    }
}