#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(ll i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()
template<typename T> bool chmax(T &x, const T &y) {return (x<y)?(x=y,true):false;};
template<typename T> bool chmin(T &x, const T &y) {return (x>y)?(x=y,true):false;};
constexpr ll MOD=1000000007;
constexpr ll INF=2e18;

int main(){
    ll n, k, p; cin >> n >> k >> p;
    VI a(n), b(n);
    REP(i,n) cin >> a[i], a[i]%=p;
    REP(i,n) cin >> b[i], b[i]%=p;
    sort(ALL(b));
    ll l=-1, r=p;
    while(r-l>1){
        ll m=(l+r)/2;
        ll sum=0;
        REP(i,n){
            if(a[i]<=m)
                sum+=upper_bound(ALL(b),m-a[i])-b.begin();
            sum+=upper_bound(ALL(b),p-max(0LL,a[i]-m))-lower_bound(ALL(b),p-a[i]);
            //cout << a[i] << " " << p-max(0LL,a[i]-m) << " " << p-a[i] << endl;
        }
        //cout << m << " " << sum << endl;
        if(sum>=k)
            r=m;
        else
            l=m;
    }
    cout << r << endl;
    return 0;
}