#include<bits/stdc++.h>

#pragma GCC optimize(3)
typedef long long ll;

using namespace std;
const int N = 2e5 + 50;

const int mod = 1e9 + 7;
int a[N];
int vis[N];

int query_mex(int l, int r) {
    for (int i = 0; i <= 2e5; i++) vis[i] = 0;
    for (int i = l; i <= r; i++) vis[a[i]] = 1;
    int p = 0;
    while (vis[p]) p++;
    return p;
}

int simulate(int n, int q, int k, int s) {
    std::mt19937 gen;
    gen.seed(s);
    int last = 0;
    while (q--) {
        int op = gen() % k;
        int i = (gen() + last) % n;
        if (!op && i) {
            std::swap(a[i - 1], a[i]);
        } else {
            int j = gen() % n;
            last ^= query_mex(std::min(i, j), std::max(i, j));
        }
    }
    return last;
}

int n, q, k, s;

void solve() {
    cin >> n >> q >> k >> s;
    for (int i = 0; i < n; i++) cin >> a[i];
    cout << simulate(n, 1, k, s) << '\n';
}


int main() {
    ios::sync_with_stdio(false), cin.tie(nullptr);
    int _ = 1;
//    cin >> _;
    for (int o = 1; o <= _; o++) {
        solve();
    }
    return 0;
}
/*
5
3 1 1 0
0 1 2
3 2 1 0
0 1 2
3 3 1 0
0 1 2
3 4 1 0
0 1 2
3 5 1 0
0 1 2
 */