#include<stdio.h>
int n,v[1000000],m[1000000];
bool ok=false;
void citire()
{
	for(int i=1;i<=n;++i)
		scanf("%d",&v[i]);
}
int main()
{
	int p=1,i,j,nr=0;
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	scanf("%d",&n);
	citire();
	for(int i=1;i<=n;++i)
	{
		j=i-1;
		if(v[i]>v[j])
			nr=nr-v[j]+v[i];
		
	}
	printf("%d",nr);
	return 0;
}