OI-codes/LibreOJ/2608/2608.cpp

#include <bits/stdc++.h>

using namespace std;

long long binpow(long long a, long long b, long long m) {
    a %= m;
    long long res = 1;
    while (b > 0) {
        if (b & 1) res = res * a % m;
        a = a * a % m;
        b >>= 1;
    }
    return res;
}

int main() {
    int n, m, k, x;
    cin >> n >> m >> k >> x;
    cout << (x % n + m % n * binpow(10, k, n) % n) % n << endl;
    return 0;
}