#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  long long sum = 0;
  long long max = 0;
  for (int i = 0; i < n; i++) {
    long long a;
    cin >> a;
    if (a > max)
      max = a;
    else
      sum = max - a;
  }
  cout << sum << endl;
}
