#include <iostream>
#include <cstdio>

using namespace std;

int main ()
{
	FILE *fin = fopen ("operatii.in", "r");
	FILE *fout = fopen ("operatii.out", "w");
	long N, i, XCurent, XPrecedent=0;
	long long S=0;
	fscanf (fin, "%ld", &N);
	for (i=0; i<N; i++)
	{
		fscanf (fin, "%ld", &XCurent);
		if (XCurent>XPrecedent)
		{
			S+=(XCurent-XPrecedent);
		}
		XPrecedent=XCurent;
	}
	fprintf (fout, "%lld\n", S);
	fclose (fin);
	fclose (fout);
	return 0;
}