#include<bits/stdc++.h>
using namespace std;
const int MaxN = 1e6 + 5;
long long n, a[MaxN];
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
freopen("file.inp", "r", stdin);
freopen("file.out", "w", stdout);
cin >> n;
long long mx = 0;
for (int i = 1; i <= n; i++)
{
cin >> a[i];
mx = max(mx, a[i]);
}
long long res = mx - a[1];
for (int i = 2; i <= n; i++)
{
res += max(0LL, a[i - 1] - a[i]);
}
cout << res << "\n";
return 0;
}
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