#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
int n, m, popcount[32777]; long long a[19];
int main() {
	cin >> n >> m;
	for (int i = 0; i < n; i++) cin >> a[i];
	long long ret = 1LL << 60;
	for (int i = 0; i < 1 << n; i++) {
		popcount[i] = popcount[i >> 1] + (i & 1);
		if (i % 2 == 0 || popcount[i] < m) continue;
		vector<int> b;
		for (int j = 0; j < n; j++) {
			if (i & (1 << j)) b.push_back(j);
		}
		b.push_back(n);
		long long sum = 0, l = 0;
		for (int j = 0; j < b.size() - 1; j++) {
			l = max(l + 1, *max_element(a + b[j], a + b[j + 1]));
			sum += l - a[b[j]];
		}
		ret = min(ret, sum);
	}
	cout << ret << endl;
	return 0;
}

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