Artihmetic progression

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<double> vd;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<pi> vp;
typedef vector<pl> vpl;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cerr.tie(nullptr);

    int n, k;
    cin >> n >> k;

    vi a(n);
    for (auto& i : a)
        cin >> i;

    int res = INT32_MAX;
    for (int i = 0; i < n; ++i){
        int s = a[i], sol = 0;
        for (int j = i + 1; j < n; ++j){
            s += k;
            if (a[j] != s)
                ++sol;
        }
        s = a[i];
        for (int j = i - 1; j > -1; --j){
            s -= k;
            if (a[j] != s)
                ++sol;
        }
        res = min(sol, res);
    }

    cout << res << '\n';
}