#include<bits/stdc++.h>
#define int long long
using namespace std;
void ts(){cout<<"IAKIOI\n";}
inline int read(){
	int n=0,f=1,ch=getchar();
	while(ch<'0'||ch>'9'){
		if(ch=='-')f=-1;
		ch=getchar();
	}
	while(ch>='0'&&ch<='9'){
		n=n*10+ch-'0';
		ch=getchar();
	}
	return n*f;
}
int n;
int a[300005];
int f[300005];
int find(int x){return f[x]==x?x:f[x]=find(f[x]);}
struct edg{
	int w,u,v;
}p[1000005];
bool cmp(edg a,edg b){return a.w<b.w;}
signed main(){
	n=read();
	for(int i=1;i<=n;i++)a[i]=read();
	for(int i=1;i<=n;i++)f[i]=i;
	int tot=0;
	for(int i=1;i<=n;i++){
		for(int j=i+1;j<=n;j++){
			if(i<j&&a[i]>a[j])p[++tot]={a[i]-a[j],i,j};
		}
	}
	sort(p+1,p+tot+1,cmp);
	int res=0;
	for(int i=1;i<=tot;i++){
		if(find(p[i].u)!=find(p[i].v)){
			res+=p[i].w,f[find(p[i].u)]=find(p[i].v);
		}
	}
	cout<<res<<"\n";
	return 0;
}
//look at my code
//my code is amazing