#line 1 "B.cpp"
// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
using namespace std;

using ll = long long;
using ull = unsigned long long;
template <class T>
using pq = priority_queue<T>;
template <class T>
using qp = priority_queue<T, vector<T>, greater<T>>;
#define vec(T, A, ...) vector<T> A(__VA_ARGS__);
#define vvec(T, A, h, ...) vector<vector<T>> A(h, vector<T>(__VA_ARGS__));
#define vvvec(T, A, h1, h2, ...) vector<vector<vector<T>>> A(h1, vector<vector<T>>(h2, vector<T>(__VA_ARGS__)));

#define endl "\n"
#define spa ' '
#define len(A) A.size()
#define all(A) begin(A), end(A)

#define fori1(a) for(ll _ = 0; _ < (a); _++)
#define fori2(i, a) for(ll i = 0; i < (a); i++)
#define fori3(i, a, b) for(ll i = (a); i < (b); i++)
#define fori4(i, a, b, c) for(ll i = (a); ((c) > 0 || i > (b)) && ((c) < 0 || i < (b)); i += (c))
#define overload4(a, b, c, d, e, ...) e
#define fori(...) overload4(__VA_ARGS__, fori4, fori3, fori2, fori1)(__VA_ARGS__)

#define enum1(A) fori(A.size())
#define enum2(a, A) for(auto a:A)
#define enum3(i, a, A) for(ll i = 0, a = A[i]; i < A.size(); a = A[++i])
#define enum4(i, a, A, s) for(ll i = s, a = A[i - s]; i - s < A.size(); a = A[++i - s])
#define enum(...) overload4(__VA_ARGS__, enum4, enum3, enum2, enum1)(__VA_ARGS__)

#define zip4(a, b, A, B) if(min(A.size(), B.size()) >= 1) for(ll _ = 0, a = A[_], b = B[_]; _ < min(A.size(), B.size()); a = A[++_], b = B[_])
#define enumzip5(i, a, b, A, B) if(min(A.size(), B.size()) >= 1) for(ll i = 0, a = A[i], b = B[i]; i < min(A.size(), B.size()); a = A[++i], b = B[i])
#define enumzip6(i, a, b, A, B, s) if(min(A.size(), B.size()) >= 1) for(ll i = s, a = A[i - s], b = B[i - s]; i - s < min(A.size(), B.size()); a = A[++i - s], b = B[i - s])
#define overload6(a, b, c, d, e, f, g, ...) g
#define zip(...) overload6(__VA_ARGS__, enumzip6, enumzip5, zip4, _, _, _)(__VA_ARGS__)

#define INT(...) int __VA_ARGS__; inp(__VA_ARGS__);
#define LL(...) ll __VA_ARGS__; inp(__VA_ARGS__);
#define STRING(...) string __VA_ARGS__; inp(__VA_ARGS__);
#define CHAR(...) char __VA_ARGS__; inp(__VA_ARGS__);
#define VEC(T, A, n) vector<T> A(n); inp(A);
#define VVEC(T, A, n, m) vector<vector<T>> A(n, vector<T>(m)); inp(A);

const ll MOD1 = 1000000007;
const ll MOD9 = 998244353;

template<class T> auto min(const T& a){
    return *min_element(all(a));
}
template<class T> auto max(const T& a){
    return *max_element(all(a));
}
template <class T, class S>
inline bool chmax(T &a, const S &b) {
  return (a < b ? a = b, 1 : 0);
}
template <class T, class S>
inline bool chmin(T &a, const S &b) {
  return (a > b ? a = b, 1 : 0);
}

void FLUSH(){cout << flush;}
void print(){cout << endl;}
template <class Head, class... Tail>
void print(Head &&head, Tail &&... tail) {
    cout << head;
    if (sizeof...(Tail)) cout << spa;
    print(forward<Tail>(tail)...);
}
template<typename T>
void print(vector<T> &A){
    int n = A.size();
    for(int i = 0; i < n; i++){
        cout << A[i];
        if(i == n - 1) cout << endl;
        else cout << spa;
    }
}
template<typename T>
void print(vector<vector<T>> &A){
    for(auto &row: A) print(row);
}
template<typename T, typename S>
void print(pair<T, S> &A){
    cout << A.first << spa << A.second << endl;
}
template<typename T, typename S>
void print(vector<pair<T, S>> &A){
    for(auto &row: A) print(row);
}
template<typename T, typename S>
void prisep(vector<T> &A, S sep){
    int n = A.size();
    for(int i = 0; i < n; i++){
        cout << A[i];
        if(i == n - 1) cout << endl;
        else cout << sep;
    }
}
template<typename T, typename S>
void priend(T A, S end){
    cout << A << end;
}
template<typename T>
void priend(T A){
    priend(A, spa);
}
template<class... T>
void inp(T&... a){
    (cin >> ... >> a);
}
template<typename T>
void inp(vector<T> &A){
    for(auto &a:A) cin >> a;
}
template<typename T>
void inp(vector<vector<T>> &A){
    for(auto &row:A) inp(row);
}
template<typename T, typename S>
void inp(pair<T, S> &A){
    inp(A.first, A.second);
}
template<typename T, typename S>
void inp(vector<pair<T, S>> &A){
    for(auto &row: A) inp(row.first, row.second);
}

template<typename T>
T sum(vector<T> &A){
    T tot = 0;
    for(auto a:A) tot += a;
    return tot;
}

#line 2 "Library/C++/math/pollard_rho.hpp"

#line 2 "Library/C++/math/modpow.hpp"

template<typename T>
T modpow(T a, long long b, T MOD){
    T ret = 1;
    while(b > 0){
        if(b & 1){
            ret *= a;
            ret %= MOD;
        }
        a *= a;
        a %= MOD;
        b >>= 1;
    }
    return ret;
}
#line 3 "Library/C++/math/millerRabin.hpp"

bool isPrime(long long n){
    if(n <= 1) return false;
    else if(n == 2) return true;
    else if(n % 2 == 0) return false;

    long long A[7] = {2, 325, 9375, 28178, 450775, 9780504, 1795265022};
    long long s = 0;
    long long d = n - 1;
    while(d % 2 == 0){
        d /= 2;
        s++;
    }

    for(auto a: A){
        if(a % n == 0) return true;
        long long x = modpow<__int128_t>(a, d, n);
        if(x != 1){
            bool ng = true;
            for(int i = 0; i < s; i++){
                if(x == n - 1){
                    ng = false;
                    break;
                };
                x = __int128_t(x) * x % n;
            }
            if(ng) return false;
        }
    }
    return true;
}
#line 4 "Library/C++/math/pollard_rho.hpp"

long long pollard(long long N) {
    if (N % 2 == 0) return 2;
    if (isPrime(N)) return N;

    auto f = [&](long long x) -> long long {
        return (__int128_t(x) * x + 1) % N;
    };
    long long step = 0;
    while (true) {
        ++step;
        long long x = step, y = f(x);
        while (true) {
            long long p = gcd(y - x + N, N);
            if (p == 0 || p == N) break;
            if (p != 1) return p;
            x = f(x);
            y = f(f(y));
        }
    }
}

vector<long long> primefact(long long N) {
    if (N == 1) return {};
    long long p = pollard(N);
    if (p == N) return {p};
    vector<long long> left = primefact(p);
    vector<long long> right = primefact(N / p);
    left.insert(left.end(), right.begin(), right.end());
    sort(left.begin(), left.end());
    return left;
}
#line 3 "Library/C++/math/totient.hpp"

template<typename T>
T totient(T n){
    vector<T> primes = primefact(n);
    primes.erase(unique(primes.begin(), primes.end()), primes.end());
    for(auto p:primes){
        n /= p;
        n *= p - 1;
    }
    return n;
}
#line 142 "B.cpp"

void solve(){
    LL(m, d, n, b);
    if(n == 0){
        if(m % b != 10) print(m % b);
        else print('A');
        return;
    }
    if(m == 0 && d % b == 0){
        print(1);
        return;
    }

    ll MOD = b * totient(b);
    vec(int, A, 0);
    vec(bool, used, 2 * MOD, false);
    d %= MOD;
    if(m == 0){
        n--;
        m = 1;
    }
    if(m >= MOD){
        m %= MOD;
        m += MOD;
    }

    auto nex=[&](long long m){
        long long nm = modpow(m + d, m, MOD);
        long long x = 1;
        ll c = m;
        while(c--){
            x *= m + d;
            if(x > nm){
                nm += MOD;
                break;
            }
        }
        return nm;
    };

    while(!used[m]){
        used[m] = true;
        A.push_back(m);
        m = nex(m);
    }
    if(n < len(A)){
        if(A[n] % b != 10) print(A[n] % b);
        else print('A');
        return;
    }
    n -= len(A);
    int loop;
    enum(i, a, A){
        if(a == m){
            loop = len(A) - i;
            break;
        }
    }
    n %= loop;
    fori(n) m = nex(m);
    if(m % b != 10)print(m % b);
    else print('A');
}

int main(){
    cin.tie(0)->sync_with_stdio(0);
    int t;
    t = 1;
    // cin >> t;
    while(t--) solve();
    return 0;
}