#include<fstream>
using namespace std;
ifstream f("operatii.in");
ofstream g("operatii.out");
long long nr,a,b,n;
int main (){
	
	f>>n;
	
	for(;n;n--){
		f>>a;
		if(a>b)
			nr+=a-b;
		b=a;
	}
	g<<nr<<"\n";
	return 0;
}