//Lasha Bukhnikashvili
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<map>
#include<queue>
#include<string>
#define Pi 3.14159265358
#define mod9 %1000000009
#define INF 1000000000
#define mod7 1000000007
#define LL  long long
#define time clock()/(double)CLOCKS_PER_SEC
using namespace std;

  long long m,lx,p,q,rx,mid,n,ra,i,j;
  long double l,r,ind,ans,c[3000001],x[3000001];
int main(){

     cin>>m>>n>>ra;
     for (i=1;i<=m;i++)
        cin>>c[i];
    for (i=1;i<=n;i++)
        cin>>x[i];
    ind=c[1];
    for (i=1;i<=n;i++){
        l=x[i]-sqrt(ra*ra-1); r=x[i]+sqrt(ra*ra+1);
        lx=1; rx=m;
        while (lx<rx){
            mid=(lx+rx)/2;
            if (c[mid]<l) lx=mid+1; else rx=mid;
        };
        p=lx;
        lx=1; rx=m;
        while (lx<rx){
            if (rx-lx==1){
                if (c[rx]<=r) lx=rx; else rx=lx;
                break;
            };
            mid=(lx+rx)/2;
            if (c[mid]<=r) lx=mid; else rx=mid-1;
        };
        q=lx;
        if (ind>=c[p] && ind<=c[q]) continue;
        if (ind<c[p]) ans+=c[p]-ind,ind=c[p];
         else ans+=ind-c[q],ind=c[q];
    };
    cout<<fixed<<setprecision(1)<<ans;
 return 0;
}