#include<stdio.h>

FILE*f=fopen("operatii.in","r");
FILE*g=fopen("operatii.out","w");

int n,x,i,y;
long long rez;

int main () {
	
	fscanf( f , "%d" , &n ) ;
	
	for ( i = 1 ; i <= n ; ++i ){
		
		fscanf ( f , "%d" , &x ) ;
		
		if ( x > y )
			rez = rez + x - y ;
		
		y = x ;
		
	}
	
	fprintf( g , "%lld\n" , rez );
	
	fclose(f);
	fclose(g);
	
	return 0;
}