#include <stdio.h>
int e[1000005];
int main()
{
	int n,a,i,j,d=0;
	FILE *f1,*f2;
	f1=fopen("operatii.in","r");
	f2=fopen("operatii.out","w");
	fscanf(f1,"%d",&n);
	for(i=1;i<=n;i++)
	{
		fscanf(f1,"%d",&e[i]);
	}
	for(i=1;i<=n-1;i++)
	{
		if(e[i]<e[i+1])
			d=d+e[i+1]-e[i];
	
	}
	fprintf(f2,"%d",d);
	fclose(f1);
	fclose(f2);

	return 0;
}