#include <bits/stdc++.h>

using i64 = long long;

constexpr int L = 1 << 30;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int n, k;
    std::cin >> n >> k;
    
    int seed, add;
    std::cin >> seed >> add;
    std::vector<int> a(n);
    for (int i = 0; i < n; i++) {
        seed = (1LL * seed * 239017 + add) % L;
        a[i] = seed;
    }
    
    std::sort(a.begin(), a.end());
    if (n >= 100) {
        a.resize(2 * n);
        for (int i = 0; i < n; i++) {
            a[n + i] = a[i] + L;
        }
        std::vector<i64> pre(2 * n + 1);
        for (int i = 0; i < 2 * n; i++) {
            pre[i + 1] = pre[i] + a[i];
        }
        
        auto get = [&](int l, int r) {
            int m = (l + r - 1) / 2;
            i64 res = 0;
            res += 1LL * a[m] * (m - l) - (pre[m] - pre[l]);
            res += (pre[r] - pre[m]) - 1LL * a[m] * (r - m);
            return res;
        };
        auto ans = *std::ranges::partition_point(std::ranges::iota_view(0LL, i64(1E18)),
            [&](i64 x) {
                std::vector<int> mx(2 * n);
                for (int i = 0, j = 0; i < 2 * n; i++) {
                    while (j < 2 * n && get(i, j + 1) <= x) {
                        j++;
                    }
                    mx[i] = j;
                }
                for (int i = 0; i < 2 * n / k; i++) {
                    int v = i;
                    for (int j = 0; j < k; j++) {
                        v = mx[v];
                        if (v >= i + n) {
                            return false;
                        }
                    }
                }
                return true;
            });
        std::cout << ans << "\n";
        return 0;
    }
    
    std::vector f(n, std::vector<i64>(n + 1));
    for (int i = 0; i < n; i++) {
        for (int j = 1; j <= n; j++) {
            f[i][j] = 1E18;
            for (int x = 0; x < j; x++) {
                i64 res = 0;
                for (int y = 0; y < j; y++) {
                    int d = std::abs(a[(i + x) % n] - a[(i + y) % n]);
                    res += std::min(d, L - d);
                }
                f[i][j] = std::min(f[i][j], res);
            }
        }
    }
    
    auto ans = *std::ranges::partition_point(std::ranges::iota_view(0LL, i64(1E18)),
        [&](i64 x) {
            bool ok = false;
            for (int i = 0; i < n; i++) {
                if (!ok) {
                    int l = 0;
                    int v = 0;
                    while (l < n) {
                        int r = l;
                        while (r < n && f[(i + l) % n][r + 1 - l] <= x) {
                            r++;
                        }
                        l = r;
                        v++;
                    }
                    if (v <= k) {
                        ok = true;
                    }
                }
            }
            return !ok;
        });
    std::cout << ans << "\n";
    
    return 0;
}