#include <bits/stdc++.h>   using namespace std;   const long long int nax = 1e5 + 5;   void solve() {     long long int n;     cin >> n;     vector<long long int> a(n);     for (auto &x : a) cin >> x;     long long int sum = 0, mx = 0;     for (long long int i = 0; i < n - 1; i++) {       sum += max((long long int)0, a[i] - a[i + 1]);     }     cout << sum <<   n ;   }   int32_t main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     long long int t = 1;     cin >> t;     while (t--) solve();     return 0;   }   