#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t, n, m, k, x, l, r, i, sum = 0, y, sx, sy, ex, ey, ans = 0;
  cin >> n;
  int arr[n];
  for (int i = 0; i < n; i++) cin >> arr[i];
  for (int i = 1; i < n; i++)
    if (arr[i] > arr[i - 1]) ans += arr[i] - arr[i - 1];
  cout << ans;
}
