#include <stdio.h>


 int a[1000001],n,nr,i,j,k,min;
 long p;

 int main()
  {FILE *fin,*fout;


  fin=fopen("operatii.in","r");
  fscanf(fin,"%d",&n);
  for (i=1;i<=n;i++)
       fscanf(fin,"%d",&a[i]);
  fclose(fin);

  p=0;
  nr=1;
  while (nr==1)
     {nr=0;
      i=1;
      while (i<=n)
        {if (a[i]==0) i++;
                 else {nr=1;
                       j=i;
                       min=a[i];
                       while (a[j]!=0)
                           {if (a[j]<min) min=a[j];
                            j++;
                            }
                       for (k=i;k<j;k++) a[k]=a[k]-min;
                       i=j;
                       p+=min;
                       }
         }
      }

   fout=fopen("operatii.out","w");
   fprintf(fout,"%ld",p);
   fclose(fout);

   return 0;

   }