#include <iostream>
#include <map>
#include <cassert>
#include <algorithm>
using namespace std;

long long N, K, P;
long long A[1 << 18], B[1 << 18];
long long SB[20000009];

bool solve(long long border) {
	long long sum = 0;
	for (int i = 1; i <= N; i++) {
		long long cl = P - A[i] - 1LL;
		long long cr = P - A[i] + border;
		sum += SB[cr] - SB[cl];
	}
	if (sum >= K) return true;
	return false;
}

int main() {
	// Step #1. Input
	cin >> N >> K >> P;
	for (int i = 1; i <= N; i++) cin >> A[i];
	for (int i = 1; i <= N; i++) cin >> B[i];
	assert(1 <= N && N <= 100000);
	assert(1 <= K && K <= N * N);
	assert(2 <= P && P <= 10000000);
	for (int i = 1; i <= N; i++) assert(0 <= A[i] && A[i] < P);
	for (int i = 1; i <= N; i++) assert(0 <= B[i] && B[i] < P);

	// Step #2. Prepare
	for (int i = 1; i <= N; i++) SB[B[i]] += 1;
	for (int i = 1; i <= N; i++) SB[B[i] + P] += 1;
	for (int i = 1; i <= 2 * P; i++) SB[i] += SB[i - 1];

	// Step #3. Binary Search
	long long cl = 0, cr = P, cm, minx = (1LL << 60);
	for (int i = 0; i < 30; i++) {
		cm = (cl + cr) / 2LL;
		bool I = solve(cm);
		if (I == true) { minx = min(minx, cm); cr = cm; }
		else { cl = cm; }
	}

	// Step #4. Output
	cout << minx << endl;
	return 0;
}