#include<bits/stdc++.h>
using namespace std;
int f[1000006],  b[2000006], n, m, ans;
struct node {
	int num, name;
} a[1000006];
int readNum() {
	int x = 0, f = 1;
	char ch = getchar();
	while (ch < '0' || ch > '9') {
		if (ch == '-') f = -1;
		ch = getchar();
	}
	while (ch >= '0' && ch <= '9') {
		x = (x << 1) + (x << 3) + (ch ^ 48);
		ch = getchar();
	}
	return x * f;
}
void writeNum(int x) {
	if (x < 0) {
		putchar('-');
		x = -x;
	}
	if (x > 9) {
		writeNum(x / 10);
	}
	putchar(x % 10 + '0');
}
inline void in(int& p) {
	p = readNum();
}
inline void out(int p) {
	writeNum(p);
}
inline int lowbit(int p) {
	return p & -p;
}
inline void add(int p, int q) {
	while (p <= 2 * n) {
		b[p] = max(b[p], q);
		p += lowbit(p);
	}
}
inline int query(int p) {
	if (p <= 0) return 0;
	int cnt = 0;
	while (p >= 1) {
		cnt = max(cnt, b[p]);
		p -= lowbit(p);
	}
	return cnt;
}
bool cmp(node p, node q) {
	return (p.num == q.num) ? p.name < q.name : p.num < q.num;
}
int main() {
	in(n);
	in(m);
	for (int i = 1; i <= n; i++) {
		in(a[i].num);
		a[i].num = i - a[i].num;
		a[i].name = i;
	}
	sort(a + 1, a + n + 1, cmp);
	for (int i = 1; i <= n; i++) {
		if (a[i].num < 0) {
			f[i] = 0;
			continue;
		}
		f[i] = query(a[i].name - a[i].num) + 1;
		add(a[i].name - a[i].num + 1, f[i]);
		if (a[i].num <= m && n - a[i].name >= m - a[i].num) {
			ans = max(ans, f[i]);
		}
	}
	out(ans);
	return 0;
}