#include <cstdio>

typedef long long i64;

int max(int a, int b) {
  return a > b ? a : b;
}

int main() {
  int n, x, y;
  i64 ans;
  FILE *f = fopen("operatii.in", "r");
  fscanf(f, "%d", &n);
  ans = 0;
  for (int i = 0; i < n; ++i) {
    fscanf(f, "%d", &x);
    ans += max(x - y, 0);
    y = x;
  }
  fclose(f);
  f = fopen("operatii.out", "w");
  fprintf(f, "%lld\n", ans);
  fclose(f);
  return 0;
}