#include <fstream>

using namespace std;

const char InFile[]="operatii.in";
const char OutFile[]="operatii.out";

ifstream fin(InFile);
ofstream fout(OutFile);

long long N,curr,last;

int main()
{
	long long sol=0;
	fin>>N;
	fin>>curr;
	for(register int i=2;i<=N;++i)
	{
		last=curr;
		fin>>curr;

		if(curr<last)
		{
			sol+=last-curr;
		}
	}
	fin.close();

	sol+=curr;
	
	fout<<sol;
	fout.close();
	return 0;
}