#include <fstream.h>
#include<iostream.h>
unsigned long n,m,a,b,i;
int main()
{ifstream in("operatii.in");
ofstream out("operatii.out");
in>>n;
for (i=1;i<=n;i++)
	{in>>b;
	if(b!=0) 
		if(b>a) m=m+(b-a);
	a=b;}
in.close();
out<<m<<endl;
out.close();
return 0;
}