#include<stdio.h>

#define INPUT "operatii.in"
#define OUTPUT "operatii.out"

FILE *fin = fopen(INPUT, "r"), *fout = fopen(OUTPUT, "w");

int main()
{
  long N, Ant, Cur;
  long Final = 0;

  fscanf(fin, "%ld", &N);

  fscanf(fin, "%ld", &Ant);

  Final = Ant;
  
  for(long i = 2; i <= N; ++i)
  {
    fscanf(fin, "%ld", &Cur);
    if(Cur > Ant) Final += (Cur - Ant);
    Ant = Cur;
  }

  fprintf(fout, "%ld\n", Final);

  fclose(fin);
  fclose(fout);

  return 0;
}