#include<bits/stdc++.h>
using namespace std;
int main() {
int t;
cin >> t;
while (t--) {
int n, k;
cin >> n >> k;
vector<int> heights(n);
for (int i = 0; i < n; i++) {
cin >> heights[i];
}
vector<int> leftMax(n), rightMax(n);
leftMax[0] = heights[0];
rightMax[n - 1] = heights[n - 1];
for (int i = 1; i < n; i++) {
leftMax[i] = max(leftMax[i - 1], heights[i]);
}
for (int i = n - 2; i >= 0; i--) {
rightMax[i] = max(rightMax[i + 1], heights[i]);
}
long long totalWater = 0;
for (int i = 0; i < n; i++) {
totalWater += max(0, min(leftMax[i], rightMax[i]) - heights[i]);
}
cout << totalWater << endl;
}
return 0;
}