#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <chrono>
#include <cmath>
#include <complex>
#include <deque>
#include <forward_list>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using lint = long long;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template <typename T, typename V>
void ndarray(vector<T>& vec, const V& val, int len) { vec.assign(len, val); }
template <typename T, typename V, typename... Args> void ndarray(vector<T>& vec, const V& val, int len, Args... args) { vec.resize(len), for_each(begin(vec), end(vec), [&](T& v) { ndarray(v, val, args...); }); }
template <typename T> bool chmax(T &m, const T q) { return m < q ? (m = q, true) : false; }
template <typename T> bool chmin(T &m, const T q) { return m > q ? (m = q, true) : false; }
const std::vector<std::pair<int, int>> grid_dxs{{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
int floor_lg(long long x) { return x <= 0 ? -1 : 63 - __builtin_clzll(x); }
template <class T1, class T2> T1 floor_div(T1 num, T2 den) { return (num > 0 ? num / den : -((-num + den - 1) / den)); }
template <class T1, class T2> std::pair<T1, T2> operator+(const std::pair<T1, T2> &l, const std::pair<T1, T2> &r) { return std::make_pair(l.first + r.first, l.second + r.second); }
template <class T1, class T2> std::pair<T1, T2> operator-(const std::pair<T1, T2> &l, const std::pair<T1, T2> &r) { return std::make_pair(l.first - r.first, l.second - r.second); }
template <class T> std::vector<T> sort_unique(std::vector<T> vec) { sort(vec.begin(), vec.end()), vec.erase(unique(vec.begin(), vec.end()), vec.end()); return vec; }
template <class T> int arglb(const std::vector<T> &v, const T &x) { return std::distance(v.begin(), std::lower_bound(v.begin(), v.end(), x)); }
template <class T> int argub(const std::vector<T> &v, const T &x) { return std::distance(v.begin(), std::upper_bound(v.begin(), v.end(), x)); }
template <class IStream, class T> IStream &operator>>(IStream &is, std::vector<T> &vec) { for (auto &v : vec) is >> v; return is; }

template <class OStream, class T> OStream &operator<<(OStream &os, const std::vector<T> &vec);
template <class OStream, class T, size_t sz> OStream &operator<<(OStream &os, const std::array<T, sz> &arr);
template <class OStream, class T, class TH> OStream &operator<<(OStream &os, const std::unordered_set<T, TH> &vec);
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const pair<T, U> &pa);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::deque<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::set<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::multiset<T> &vec);
template <class OStream, class T> OStream &operator<<(OStream &os, const std::unordered_multiset<T> &vec);
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const std::pair<T, U> &pa);
template <class OStream, class TK, class TV> OStream &operator<<(OStream &os, const std::map<TK, TV> &mp);
template <class OStream, class TK, class TV, class TH> OStream &operator<<(OStream &os, const std::unordered_map<TK, TV, TH> &mp);
template <class OStream, class... T> OStream &operator<<(OStream &os, const std::tuple<T...> &tpl);

template <class OStream, class T> OStream &operator<<(OStream &os, const std::vector<T> &vec) { os << '['; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <class OStream, class T, size_t sz> OStream &operator<<(OStream &os, const std::array<T, sz> &arr) { os << '['; for (auto v : arr) os << v << ','; os << ']'; return os; }
template <class... T> std::istream &operator>>(std::istream &is, std::tuple<T...> &tpl) { std::apply([&is](auto &&... args) { ((is >> args), ...);}, tpl); return is; }
template <class OStream, class... T> OStream &operator<<(OStream &os, const std::tuple<T...> &tpl) { os << '('; std::apply([&os](auto &&... args) { ((os << args << ','), ...);}, tpl); return os << ')'; }
template <class OStream, class T, class TH> OStream &operator<<(OStream &os, const std::unordered_set<T, TH> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::deque<T> &vec) { os << "deq["; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T> OStream &operator<<(OStream &os, const std::unordered_multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <class OStream, class T, class U> OStream &operator<<(OStream &os, const std::pair<T, U> &pa) { return os << '(' << pa.first << ',' << pa.second << ')'; }
template <class OStream, class TK, class TV> OStream &operator<<(OStream &os, const std::map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
template <class OStream, class TK, class TV, class TH> OStream &operator<<(OStream &os, const std::unordered_map<TK, TV, TH> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
#ifdef HITONANODE_LOCAL
const string COLOR_RESET = "\033[0m", BRIGHT_GREEN = "\033[1;32m", BRIGHT_RED = "\033[1;31m", BRIGHT_CYAN = "\033[1;36m", NORMAL_CROSSED = "\033[0;9;37m", RED_BACKGROUND = "\033[1;41m", NORMAL_FAINT = "\033[0;2m";
#define dbg(x) std::cerr << BRIGHT_CYAN << #x << COLOR_RESET << " = " << (x) << NORMAL_FAINT << " (L" << __LINE__ << ") " << __FILE__ << COLOR_RESET << std::endl
#define dbgif(cond, x) ((cond) ? std::cerr << BRIGHT_CYAN << #x << COLOR_RESET << " = " << (x) << NORMAL_FAINT << " (L" << __LINE__ << ") " << __FILE__ << COLOR_RESET << std::endl : std::cerr)
#else
#define dbg(x) ((void)0)
#define dbgif(cond, x) ((void)0)
#endif

// https://trap.jp/post/1444/
constexpr uint32_t totient(uint32_t x){
    uint32_t ans = x;
    for(uint32_t i = 2; i * i <= x; i++) if(x % i == 0){
        ans /= i;
        ans *= i - 1;
        do x /= i; while(x % i == 0);
    }
    if(x != 1){
        ans /= x;
        ans *= x - 1;
    }
    return ans;
}
template<uint32_t P> struct Modint{
    static_assert(P < 0x80000000, "P must be smaller than 2^31");
    uint32_t a;
    Modint<totient(P)> b;
private:
    static uint32_t mod(uint64_t x){
        if(x < P * 2) return uint32_t(x);
        return uint32_t(x % P) + P;
    }
    static uint32_t mul(uint32_t a, uint32_t b){
        return mod(uint64_t(a) * b);
    }
    static uint32_t pow(uint32_t a, uint32_t b){
        uint32_t ans = 1;
        while(b){
            if(b & 1) ans = mul(ans, a);
            a = mul(a, a);
            b >>= 1;
        }
        return ans;
    }
public:
    Modint(uint64_t x): a(mod(x)), b(x){}
    Modint(uint32_t a, Modint<totient(P)> b): a(a), b(b){}
    uint32_t val() const {
        if(a < P) return a;
        return a - P;
    }
    Modint& operator*=(const Modint& other){
        a = mul(a, other.a);
        b *= other.b;
        return *this;
    }
    Modint operator*(const Modint& other) const {
        return Modint(*this) *= other;
    }
    Modint& operator+=(const Modint& other){
        a += other.a;
        if(a >= P * 2) a -= P;
        if(a >= P * 2) a -= P;
        b += other.b;
        return *this;
    }
    Modint operator+(const Modint& other) const {
        return Modint(*this) += other;
    }
    Modint pow(const Modint& other) const {
        return {pow(a, other.b.a), b.pow(other.b)};
    };

    bool operator==(const Modint &other) const { return a == other.a and b == other.b; }
};
template<> struct Modint<1>{
    uint32_t a;
    Modint(uint64_t x): a(bool(x)){}
    uint32_t val() const {
        return 0;
    }
    Modint& operator*=(const Modint& other){
        a &= other.a;
        return *this;
    }
    Modint operator*(const Modint& other) const {
        return Modint(*this) *= other;
    }
    Modint& operator+=(const Modint& other){
        a |= other.a;
        return *this;
    }
    Modint operator+(const Modint& other) const {
        return Modint(*this) += other;
    }
    Modint pow(const Modint& other) const {
        return {a || !other.a};
    }

    bool operator==(const Modint &other) const { return a == other.a; }
};

string target_nums = "0123456789A";

template <int Base> char solve(lint M, lint D, lint N) {
    vector<Modint<Base>> seq;
    seq.push_back(Modint<Base>(M));
    for (lint t = 0; t < N; ++t) {
        auto nxt = (seq.back() + Modint<Base>(D)).pow(seq.back());
        for (int s = 1000; s < t; ++s) {
            if (seq.at(s) == nxt) {
                int circ = t + 1 - s;
                const int rem = (N - t - 1) % circ;
                return target_nums.at(seq.at(s + rem).val());
            }
        }
        seq.push_back(nxt);
    }
    return target_nums.at(seq.back().val());
}

int main() {
    lint M, D, N;
    int B;
    cin >> M >> D >> N >> B;

    if (B == 2) cout << solve<2>(M, D, N) << endl;
    if (B == 3) cout << solve<3>(M, D, N) << endl;
    if (B == 4) cout << solve<4>(M, D, N) << endl;
    if (B == 5) cout << solve<5>(M, D, N) << endl;
    if (B == 6) cout << solve<6>(M, D, N) << endl;
    if (B == 7) cout << solve<7>(M, D, N) << endl;
    if (B == 8) cout << solve<8>(M, D, N) << endl;
    if (B == 9) cout << solve<9>(M, D, N) << endl;
    if (B == 10) cout << solve<10>(M, D, N) << endl;
    if (B == 11) cout << solve<11>(M, D, N) << endl;
}