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