#include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<queue>
#include<set>
using namespace std;
int N,M,K;
map<int,pair<vector<int>,vector<int> > >mp;
main()
{
	cin>>N>>M>>K;
	for(int i=0;i<N+M;i++)
	{
		int A;cin>>A;
		if(i<N)mp[A%K].first.push_back(A/K);
		else mp[A%K].second.push_back(A/K);
	}
	long ans=0;
	for(auto it=mp.begin();it!=mp.end();it++)
	{
		vector<int>B,R;
		B.swap(it->second.first);
		R.swap(it->second.second);
		if(N>M)B.swap(R);
		if(B.size()>R.size()||N==M&&B.size()!=R.size())
		{
			cout<<-1<<endl;
			return 0;
		}
		sort(B.begin(),B.end());
		priority_queue<int>LQ;
		multiset<pair<int,int> >RS,RSS;
		for(int r:R)
		{
			RS.insert(make_pair(r,0));
			RSS.insert(make_pair(r+0,0));
		}
		for(int b:B)
		{
			while(!RS.empty()&&RS.begin()->first<=b)
			{
				pair<int,int>p=*RS.begin();
				RS.erase(RS.begin());
				RSS.erase(RSS.find(make_pair(p.first+p.second,p.second)));
				LQ.push(p.first-p.second);
			}
			long l=1e15,r=1e15;
			if(!LQ.empty())l=b-LQ.top();
			if(!RSS.empty())r=RSS.begin()->first-b;
			if(l<=r)
			{
				ans+=l;
				LQ.pop();
			}
			else
			{
				ans+=r;
				pair<int,int>p=*RSS.begin();
				RSS.erase(RSS.begin());
				RS.erase(RS.find(make_pair(p.first-p.second,p.second)));
				if(l<(long)1e15)
				{
					RS.insert(make_pair(p.first-p.second,l-r));
					RSS.insert(make_pair(p.first-p.second+l-r,l-r));
				}
			}
		}
	}
	cout<<ans<<endl;
}