// LonggVu.
#include<bits/stdc++.h>
using namespace std;
// Noob C++
#define LonggVu() ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define use(x) freopen(x".inp", "r", stdin); freopen(x".out", "w", stdout);
#define fix(x) fixed << setprecision(x)
#define all(x) x.begin(), x.end()
#define mod 1000000007
#define el '\n'
#define fi first
#define se second
#define pb push_back
#define is insert
using ll = long long int;
using ld = long double;
using str = string;
 
int n;
ll a[10005], res;
void run(int pos){
	if(pos > n) return;
	int vt = pos;
	for(int i=pos+1; i<=n; i++){
		if(a[i] >= a[vt]){
			vt = i;
		}
	}
	for(int i=pos; i<vt; i++){
		res += a[vt] - a[i];
	}run(vt + 1);
}
 
int main(){
	LonggVu();
 
	int t; cin >> t;
	while(t--){
		cin >> n;
		for(int i=1; i<=n; i++){
			cin >> a[i];
		}res = 0;
		run(1);
		cout << res << el;
	}
}

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

MwoxMAoxIDIgNCA5IDE1IDUgOCAxNSA3IDkKMwoxIDIgMTAwCjQKMSAzIDEgMgo=

3
10
1 2 4 9 15 5 8 15 7 9
3
1 2 100
4
1 3 1 2