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