#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,m,MOD,a,b,ans,bik[400001],c,st,go,mid;
vector<ll> v,u;
ll f(ll mid){
    ll tot=0;
    for(int i=0;i<n;i++){
        ll A=upper_bound(u.begin(),u.end(),mid-v[i])-u.begin();
        ll B=lower_bound(u.begin(),u.end(),0-v[i])-u.begin();
        ll C=upper_bound(u.begin(),u.end(),mid-v[i]+MOD)-u.begin();
        ll D=lower_bound(u.begin(),u.end(),0-v[i]+MOD)-u.begin();
        tot+=A-B+C-D;
        //cout<<A<<" "<<B<<" "<<C<<" "<<D<<endl;
    }
    //cout<<tot<<" "<<mid<<endl;
    return tot;
}
int main(void){
    cin>>n>>m>>MOD;
    for(int i=0;i<n;i++){
        cin>>a;
        v.push_back(a%MOD);
    }
    for(int i=0;i<n;i++){
        cin>>a;
        u.push_back(a%MOD);
    }
    sort(u.begin(),u.end());
    st=-1,go=MOD-1;
    while(go-st>1){
        mid=(st+go)/2;
        ll tmp=f(mid);
        if(tmp>=m)go=mid;
        else st=mid;
    }
    cout<<go<<endl;
}