#include <algorithm>
#include <assert.h>
#include <bitset>
#include <chrono>
#include <cstring>
#include <functional>
#include <iostream>
#include <istream>
#include <map>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <random>

#define endl '\n'

using namespace std;

const int maxn = 200100;

int a[maxn], n;

int P[maxn], S[maxn];

void my_swap(int i)
{
    swap(a[i], a[i + 1]);

    P[i] = min(P[i - 1], a[i]);
    P[i + 1] = min(P[i], a[i + 1]);

    S[i + 1] = min(S[i + 2], a[i + 1]);
    S[i] = min(S[i + 1], a[i]);
}

int query_mex(int i, int j)
{
    return min(P[i - 1], S[j + 1]);
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    mt19937 gen;

    int q, s, k;
    cin >> n >> q >> k >> s;

    gen.seed(s);

    int last = 0;

    P[0] = S[n + 1] = n;

    for (int i = 1; i <= n; ++i)
    {
        cin >> a[i];
    }

    for (int i = 1; i <= n; ++i)
    {
        P[i] = min(P[i - 1], a[i]);
    }

    for (int i = n; i; --i)
    {
        S[i] = min(S[i + 1], a[i]);
    }

    while (q--)
    {
        int op = gen() % k;

        int i = (gen() + last) % n;

        if (!op && i)
        {
            my_swap(i);
        }
        else
        {
            int j = gen() % n;

            if (i > j)
                swap(i, j);

            last ^= query_mex(i + 1, j + 1);
        }
    }

    cout << last << endl;

    return 0;
}