#include <bits/stdc++.h>
#include <string>

#define rep(i,n) for(ll i=0;i < (n);i++)
#define rep2(i, s, n) for (ll i = (s); i < (n); i++)
#define rrep(i,n) for(ll i=n-1;i>=0;i--)
#define ff first
#define ss second
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

typedef long long ll;

const ll INF=1000000000000000000ll;
const ll MOD=1000000007ll;
const int MAX=5100000;

using namespace std;

// aよりもbが大きいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmax(T &a, const T& b) {
  if (a < b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}
// aよりもbが小さいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmin(T &a, const T& b) {
  if (a > b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}

ll N, K, P;
vector<ll> A, B;

bool solve(ll now){
  ll t1, t2, t3, cnt = 0;
  rep(i, N){
    t1 = now - A[i]; t2 = P - A[i]; t3 = t1 + P;
    auto itr1 = lower_bound(ALL(B), t1);
    auto itr2 = lower_bound(ALL(B), t2);
    auto itr3 = lower_bound(ALL(B), t3);
    cnt += itr1 - B.begin();
    cnt += (itr3 - B.begin()) - (itr2 - B.begin());
    if(cnt >= K){return true;}
  }
  return false;
}

int main()
{
	cin.tie(0);	ios::sync_with_stdio(false);
  ll tmp; cin >> N >> K >> P;
  rep(i, N){cin >> tmp; A.push_back(tmp);}
  rep(i, N){cin >> tmp; B.push_back(tmp);}
  sort(ALL(A)); sort(ALL(B));

  ll OK = P, NG = -1;
  while(OK - NG > 1){
    ll mid = (OK+NG)/2;
    if(solve(mid)){OK = mid;} else{NG = mid;}
  }
  cout << NG << endl;

  return 0;
}