#include <iostream.h>
#include <fstream.h>
int main()
{long int nr=0,nr1,nr2=0,n,i;
ifstream f("operatii.in");
ofstream g("operatii.out");
f>>n;
for(i=1;i<=n;i++)
	{
	f>>nr1;
	if(nr1>nr2)nr=nr+nr1-nr2;
	nr2=nr1;
	}
g<<nr;
f.close();
g.close();
return 0;
}