#include<stdio.h>
using namespace std;

 int main()
 { long long nr,n,a,i,b;
	 
	 FILE *f = fopen("operatii.in", "r");
	 FILE *g = fopen("operatii.out", "w");
	
	 nr = 0;
	 fscanf(f, "%lld", &n);
	
	 fscanf(f, "%lld", &a);
	 for( i = 2; i <= n; i++ )
		 {
			 fscanf(f, "%lld", &b);
			 if(b > a) nr += b-a;
			 a = b;
		 }
	 
	 fprintf(g, "%lld\n", nr);
	 
	 fclose(f);
	 fclose(g);
	 return 0;
 }