#include <stdio.h>


 long n,i,y,x;
 long p;

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


  fin=fopen("operatii.in","r");
  fscanf(fin,"%ld",&n);
  p=0;
  x=0;
  fscanf(fin,"%ld",&y);
  for (i=2;i<=n;i++)
       {if (y>x) p=p+y-x;
        x=y;
        fscanf(fin,"%ld",&y);
        }
  if (y>x) p=p+y-x;
  fclose(fin);


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

  return 0;
  }