/*
TASK:ots
LANG:C++
*/   
#include <iostream>
using namespace std;
long int a[1000001];
char b[1000001];
int k,l,n;
int  srav(){
     int i,j,gap=n,v,tr;
     do{gap=(int)(gap/1.27);
        if(gap<1) gap=1;
     tr=0;
        for(i=0;i<n-gap;i++){
                             j=i+gap;
                             if(a[i]>a[j]) {v=a[i];
                                            a[i]=a[j];
                                            a[j]=v;tr=1;
                                           }
                             }   
       }while((gap>1)||(tr!=0));                                                        
           }
int main(){
    cin>>n;
    int i,j;
    for(i=0;i<n;i++) cin>>a[i];
    srav();
    for(i=0;i<(n-1);i++) b[i]=a[i+1]-a[i];
   int br=n;
   int br1=0;
   int mini;
    while(br>0){mini=30000;
               for(i=0;i<(n-1);i++) {//cout<<b[i]<<' '<<mini;
                                     //system("pause"); 
                                      if((mini>b[i])&&(b[i]!=-1)) {mini=b[i];
                                                    k=i;
                                                   }
                                    }                    
               
               br1=br1+mini;
               if(a[k]!=(-1)) br--;
               if(a[k+1]!=(-1)) br--;
               b[k]=-1;
               a[k]=-1;
               a[k+1]=-1;
              }
      cout<<br1<<endl;
      return 0;
      }
