#include <cstdio>
#define INF "operatii.in"
#define OUF "operatii.out"
#define NMAX 1000002
using namespace std;
int main()
{
	FILE *in,*out;
	int i,a1,a,n;
	long long sol=0;
	in=fopen(INF,"r");
	out=fopen(OUF,"w");

	fscanf(in,"%d",&n);a=0;
	for(i=1;i<=n;++i)
	{ 
		a1=a;
		fscanf(in,"%d",&a);
		if(a>a1) sol+=a-a1;
	}

	fprintf(out,"%lld\n",sol);
	fclose(in);fclose(out);
	return 0;
}