#include <iostream>
#include <string>
using namespace std;
#include <algorithm>
#include <vector>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <iomanip>
#include <set>
#include <map>
#include <queue>
#include <cassert>
using ll = long long;
using ld = long double;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
const ll LIMIT1 = 200010;
const ll LIMIT2 = 500010;
const ll LIMIT3 = 1000010;
const int INF = ((1<<30)-1);
const ll LLINF = (1LL<<60);
const ld EPS = (1e-14);
using cv = const void;
using P = pair<ll,ll>;
#define rep(i,n) for((i)=0;(i)<(n);(i)++)
#define per(i,n) for((i)=(n)-1;(i)>=0;(i)--)
#define ALL(a) (a).begin(),(a).end()
#define ALL2(a, n) (a),(a)+(n)
template<class T,class C> T max(T a,C b){ return std::max(a, (T)b); }
template<class T,class C> T min(T a,C b){ return std::min(a, (T)b); }
template<class T,class C> bool chmax(T &a,const C b){ if(a<(T)b){ a=(T)b;return true; } return false; }
template<class T,class C> bool chmin(T &a,const C b){ if((T)b<a){ a=(T)b;return true; } return false; }
#define zt(a,b) (max((a),(b))-min((a),(b)))
#define setpre(n) fixed << setprecision(n)
ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll lcm(ll a,ll b){return (a/gcd(a,b))*b;}
#define YES(b) (b?"YES":"NO")
#define Yes(b) (b?"Yes":"No")
#define yes(b) (b?"yes":"no")
template<class T,class C> char gl(const T a,const C b){
  T bb = (T)b;
  if(a<bb) return '<';
  else if(a>bb) return '>';
  else return '=';
}
int dx[8]={1,0,-1,0,1,-1,-1,1},dy[8]={0,1,0,-1,1,1,-1,-1};
ll modpow(ll a, ll n, ll mod) {
  ll res = 1;
  while (n > 0) {
    if (n & 1){
      res *= a; if(mod>=1) res %= mod;
    }
    a *= a; if(mod>=1) a %= mod;
    n >>= 1;
  }
  return res;
}
void initialize(){
  
}
int main(void){
  initialize();
  ll n,m,i,j,k,result=0;
  string s;
  ll p;
  
  cin >> n >> k >> p;
  k = n*n+1-k;//k番目に大きいに置き換え
  vector<ll> a(n), b(n);
  rep(i,n) cin >> a[i];
  rep(i,n) cin >> b[i];
  sort(ALL(a));
  sort(ALL(b));
  
  ll ok=0, ng=p;
  while(llabs(ok-ng)>1){//規定値以上がk個以上あるか
    ll mid = (ok+ng)/2;
    ll tmp = 0;
    for(i=0;i<n;i++){
      ll tmp2=0;
      for(j=0;j<=1;j++){
        tmp2 += distance(lower_bound(ALL(b), mid-a[i]+j*p), lower_bound(ALL(b), (j+1)*p-a[i]));
      }
      if(tmp2>=1) tmp += tmp2;
    }
    if(tmp>=k){
      ok = mid;
    }else{
      ng = mid;
    }
  }
  result = ok;
  cout << result << endl;
  return 0;
}