#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];
  int ans = 0;
  for (int i = 0; i < (n - 1); i++) {
    if (a[i] > a[i + 1]) {
      ans = a[i + 1] - a[i];
      a[i + i] = a[i];
    }
  }
  cout << ans << endl;
  return 0;
}
