#include <bits/stdc++.h>
using namespace std;

const int N = 5e4 + 5;

int n, m, p[N], id[N];
long long ans;
bitset<N> now, f[N], suf[N], pre[N];

bool cmp(int i, int j) {
	return p[i] > p[j];
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> p[i];
		id[i] = i;
	}
	sort(id + 1, id + n + 1, cmp);
	for (int i = 1; i <= n; i++) {
		int j = id[i];
		f[j] = now >> j;
		now[j] = 1;
	}
	pre[0].set();
	suf[0].set();
	for (int i = m - 1; i <= n; i += m - 1) {
		int c = min(n - i, m - 1);
		for (int j = 1; j <= c; j++) {
			pre[j] = pre[j - 1] & f[i + j];
		}
		for (int j = 1; j < m; j++) {
			suf[j] = suf[j - 1] & f[i + 1 - j];
		}
		for (int j = 1; j <= c; j++) {
			ans += (pre[j] & suf[m - j]).count();
		}
	}
	cout << ans << '\n';

	return 0;
}