F

#include <bits/stdc++.h>
#include <ext/rope>
using namespace std;
using namespace __gnu_cxx;
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef long double ld;
typedef pair<ll, ll> ii;
typedef pair<ii, ii> iii;
int MOD = 1e9 + 9;
const ld E = 1e-9;
#define null NULL
#define ms(x) memset(x, 0, sizeof(x))
#ifndef LOCAL
#define endl "\n"
#endif
#ifndef LONG_LONG_MAX
#define LONG_LONG_MAX LLONG_MAX
#endif
#define sync ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define _read(x) freopen(x, "r", stdin)
#define _write(x) freopen(x, "w", stdout)
#define files(x) _read(x ".in"); _write(x ".out")
#define filesdatsol(x) _read(x ".DAT"); _write(x ".SOL")
#define output _write("output.txt")
#define input _read("input.txt")
#define prev time_prev
#ifndef M_PI
#define M_PI acos(-1)
#endif
#define remove tipa_remove
#define next tipa_next
#define left tipa_left
#define right tipa_right
#define mod % MOD
#define y1 hello_world
unsigned char ccc;
bool _minus = false;
template<typename T>
inline T sqr(T t) {
    return (t * t);
}
inline void read(ll &n) {
    n = 0;
    _minus = false;
    while (true) {
        ccc = getchar();
        if (ccc == ' ' || ccc == '\n')
            break;
        if (ccc == '-') {
            _minus = true;
            continue;
        }
        n = n * 10 + ccc - '0';
    }
    if (_minus)
        n *= -1;
}
inline bool read(int &n) {
    n = 0;
    _minus = false;
    while (true) {
        ccc = getchar();
        if (ccc == ' ' || ccc == '\n') {
            if (ccc == '\n')
                return true;
            break;
        }
        if (ccc == '-') {
            _minus = true;
            continue;
        }
        n = n * 10 + ccc - '0';
    }
    if (_minus)
        n *= -1;
    return false;
}
char wwww[19];
int kkkk;
inline void write(ll y) {
    long long x = y;
    kkkk = 0;
    if (x < 0) {
        putchar('-');
        x *= -1;
    }
    if (!x)
        ++kkkk, wwww[kkkk] = '0';
    else
        while (x) {
            ++kkkk;
            wwww[kkkk] = char(x % 10 + '0');
            x /= 10;
        }
    for (int i = kkkk; i >= 1; --i)
        putchar(wwww[i]);
}

#ifdef LOCAL
#define DEBUG
#endif

#ifdef DEBUG
#define dbg if(1)
#else
#define dbg if(0)
#endif

const int MAX = 505;

int dp[MAX][MAX];
int c[MAX][MAX];
int ar[MAX];

int solve(int l, int r){
    if(l + 2 == r){
        c[l][r] = l + 1;
        dp[l][r] = ar[r] - ar[l];
        return ar[r] - ar[l];
    }
    if(l + 1 >= r){
        c[l][r] = l;
        return 0;
    }
    if(dp[l][r])
        return dp[l][r];
    solve(l + 1, r);
    solve(l, r - 1);
    int ans = INT_MAX;
    for(int i = c[l][r - 1]; i <= c[l + 1][r]; i++){
        int res = solve(l, i) + solve(i, r);
        if(res < ans){
            ans = res;
            c[l][r] = i;
        }
    }
    ans += ar[r] - ar[l];
    return dp[l][r] = ans;
}

int main() {
    sync;
    srand(time(NULL));
    cout.precision(10);
    cout << fixed;
#ifdef LOCAL
    input;
#else

#endif

    int t;
    cin >> t;
    while(t--){
        int len;
        int n;
        cin >> len >> n;
        for(int i = 1; i <= n; i++){
            cin >> ar[i];
        }
        ms(c);
        ar[n + 1] = len;
        ms(dp);
        cout << solve(0, n + 1) << endl;
    }

}