#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
  int n,m;cin>>n>>m;
  vector<long long> A(n),B(m);
  for(int i = 0; n > i; i++)cin>>A[i];
  for(int i = 0; m > i; i++)cin>>B[i];
  sort(A.begin(), A.end());
  sort(B.begin(), B.end());
  A.push_back(100000000001LL);
  vector<long long> C[A.size()];
  int nw = 0;
  for(int i = 0; m > i; i++){
    while(B[i]>A[nw]){
      nw++;
    }
    C[nw].push_back(B[i]);
  }
  long long ans = 0;
  for(int i = 0; n >= i; i++){
    if(C[i].size() == 0)continue;
    if(!i){
      ans += A[i]-C[i][0];
    }else if(i == n){
      ans += C[i][C[i].size()-1]-A[i-1];
    }else{
      long long mx = max(C[i][0]-A[i-1], A[i]-C[i][C[i].size()-1]);
      for(int j = 1; C[i].size() > j; j++){
        mx = max(mx,C[i][j]-C[i][j-1]);
      }
      ans += A[i]-A[i-1]-mx;
    }
  }
  cout << ans << endl;
}