#include <fstream.h>
#include <values.h>
long n,a[1000010],nr;
void citire()
{
   ifstream fin("operatii.in");
   fin>>n;
   for (long i=0;i<n;i++)
       fin>>a[i];
   fin.close();
}

void numarare()
{
    short ok=1;
  while (ok)
  {
     ok=0;
     for (long i=0;i<n;i++)
	if (a[i]!=0)
	{  ok=1;
	  long j,min=a[i];
	    for (j=i+1;j<n;j++)
	       if (a[j]==0)
		  break;
	       else
		 if (a[j]<min)
		    min=a[j];
	    nr+=min;
	    for (long y=i;y<j;y++)
		a[y]-=min;
	    break;
	}

  }
}

int main()
{
   citire();
   numarare();
   ofstream fout("operatii.out");
   fout<<nr<<"\n";
   fout.close();
   return 0;

}