#include <bits/stdc++.h>
#define pb push_back
#define all(c) c.begin(),c.end()
using namespace std;
typedef long long ll;
const ll INF64 = 1e18 + 1337;
const int INF32 = 1e9 + 228;
const int MOD = 1e9 + 7;
int n;
ll a[50000];
int main()
{
    ios_base::sync_with_stdio(0);
#ifndef __WIN32
  ifstream cin("input.txt");
  ofstream cout("output.txt");
#endif
    cin.tie(0);cout.tie(0);


    cin >> n;
    for(int i = 0; i < n; i++)
        cin >> a[i];
    ll ans = 0;
    for(int i = 0; i < n - 1; i++)
    {
        if(a[i] >= a[i + 1])
        {
            int ind = i;
            while( i < n - 1 && a[i] >= a[i + 1] ) i++;
            ans += a[ind] - a[i];
        }
    }
    bool ok = 1;
    for(int i = 0; i < n - 1; i++) if(a[i] >= a[i + 1]) ok = 0;
    if(ok)
    {
        ll maxi = a[0] - a[1];
        for(int i = 0; i < n - 1; maxi = max(maxi, a[i] - a[i+1]), i++);
        cout << maxi;
        return 0;
    }
    cout << ans;



#ifndef __WIN32
  cin.close();
  cout.close();
#endif
    return 0;
}