#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<atcoder/mincostflow>
using namespace std;
int N,M,K;
map<int,vector<pair<int,int> > >mp;
main()
{
	cin>>N>>M>>K;
	vector<int>vs;
	for(int i=0;i<N+M;i++)
	{
		int A;cin>>A;
		mp[A%K].push_back(make_pair(A,i));
		vs.push_back(A);
	}
	sort(vs.begin(),vs.end());
	vs.erase(unique(vs.begin(),vs.end()),vs.end());
	auto id=[&vs](int x){return lower_bound(vs.begin(),vs.end(),x)-vs.begin();};
	atcoder::mcf_graph<int,int>mf(vs.size()+2);
	int source=vs.size(),sink=source+1;
	for(auto it=mp.begin();it!=mp.end();it++)
	{
		vector<pair<int,int> >now;
		now.swap(it->second);
		sort(now.begin(),now.end());
		for(int i=0;i<now.size();i++)
		{
			int u=id(now[i].first);
			if(now[i].second<N)mf.add_edge(source,u,1,0);
			else mf.add_edge(u,sink,1,0);
			now[i].second=u;
		}
		for(int i=1;i<now.size();i++)if(now[i-1].first<now[i].first)
		{
			int u=now[i-1].second,v=now[i].second;
			mf.add_edge(u,v,1e9,(now[i].first-now[i-1].first)/K);
			mf.add_edge(v,u,1e9,(now[i].first-now[i-1].first)/K);
		}
	}
	pair<int,int>ans=mf.flow(source,sink);
	if(ans.first==min(N,M))cout<<ans.second<<endl;
	else cout<<-1<<endl;
}