#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 1e3 + 7;

int n, q, k, s;

int pre[N], suf[N], a[N];

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


int main() {
    scanf("%d%d%d%d", &n, &q, &k, &s);
    for(int i = 1; i <= n; i += 1)
        scanf("%d", &a[i]);
    printf("%d\n", simulate(n, a, q, k, s));
}