#include<fstream.h>
ifstream f("operatii.in");
ofstream g("operatii.out");
int main ()
{long nr=0,a=0,i,n,b;
f>>n;
for(i=1;i<=n;i++){
	 f>>b;
//	 if(b!=0){
		 if(b>a) {nr=nr+(b-a);a=b;}
//		 } else a=b;
}
g<<nr<<'\n';
f.close();g.close();return 0;}