#include<stdio.h>
int a[1000000];
int main()
{
	long long s=0;
	int n;
	FILE *in,*out;
	in=fopen("operatii.in","r");
	out=fopen("operatii.out","w");
	
	fscanf(in,"%d",&n);

	for(int i=0;i<n;++i)
	{
		fscanf(in,"%d",&a[i]);
		if(i>0)
		{
		if(a[i]>a[i-1])s+=a[i]-a[i-1];
		}	

	}
	fprintf(out,"%lld",s);
	fclose(in);
	fclose(out);
	return 0;
}