#include <iostream>
using namespace std;
int a[1000005];
int ans;
int main()
{
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	int big=0;
	for(int i=1;i<=n;i++)
	{
		if(a[i]>big)big=a[i];
		if(a[i]<big)ans=ans+big-a[i];
	}
	int i=n;
	while(a[i]<big)
	{
		ans=ans-(big-a[i]);
		i--;
	}
	cout<<ans;
	return 0;}