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