import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;

public class Main {
	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] sa = br.readLine().split(" ");
		int n = Integer.parseInt(sa[0]);
		long k = Long.parseLong(sa[1]);
		int p = Integer.parseInt(sa[2]);
		sa = br.readLine().split(" ");
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = Integer.parseInt(sa[i]) % p;
		}
		sa = br.readLine().split(" ");
		int[] b = new int[n];
		for (int i = 0; i < n; i++) {
			b[i] = Integer.parseInt(sa[i]) % p;
		}
		br.close();

		Arrays.sort(a);
		Arrays.sort(b);

		long k2 = (long) n * n - k + 1;
		int ok = 0;
		int ng = p;
		while (Math.abs(ok - ng) > 1) {
			int mid = (ok + ng) / 2;
			long cnt = 0;
			for (int i = 0; i < n; i++) {
				if (a[i] <= mid) {
					int min = mid - a[i];
					int max = p - a[i];
					int l = binarySearch(b, min);
					int r = binarySearch(b, max);
					cnt += r - l;
				} else {
					int min = 0;
					int max = p - a[i];
					int l = binarySearch(b, min);
					int r = binarySearch(b, max);
					cnt += r - l;

					min = mid + p - a[i];
					max = p;
					l = binarySearch(b, min);
					r = binarySearch(b, max);
					cnt += r - l;
				}
			}
			if (cnt >= k2) {
				ok = mid;
			} else {
				ng = mid;
			}
		}
		System.out.println(ok);
	}

	static int binarySearch(int[] array, int val) {
		int ok = array.length;
		int ng = -1;
		while (Math.abs(ok - ng) > 1) {
			int mid = (ok + ng) / 2;
			if (array[mid] >= val) {
				ok = mid;
			} else {
				ng = mid;
			}
		}
		return ok;
	}
}