#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> a(N);
  for (int i = 0; i < N; i++) cin >> a[i];
  int sum = 0;
  for (int i = 1; i < N; i++)
    if (a[i] > a[i - 1]) sum += a[i] - a[i - 1];
  cout << sum << endl;
  return 0;
}
