#include <bits/stdc++.h>
using namespace std;
int a[501000], ch[501000], fa[501000], dp[501000] = {0};
int find (int x) {
return fa[x] == x ? x : fa[x] = find (fa[x]);
}
void merge (int i, int j) {
i = find(i), j = find(j);
if (i == j) return;
fa[i] = j;
if (ch[i] == 3 or ch[j] == 3) ch[j] = min(ch[i], ch[j]);
else if (ch[i] != ch[j]) {
cout << "0\n";
exit(0);
}
}
void f(int i, int val) {
i = find(i);
if (ch[i] == 3) ch[i] = val;
else if (ch[i] != val) {
cout << "0\n";
exit(0);
}
}
int main () {
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) fa[i] = i, ch[i] = 3;
for (int i = 1; i + k - 1 <= n; i++) cin >> a[i];
for (int i = 2; i + k - 1 <= n; i++) {
int dif = a[i] - a[i - 1];
if (dif == 0) merge(i - 1, i + k - 1);
else if (dif == 1) f(i + k - 1, 1), f(i - 1, 0);
else f(i + k - 1, 0), f(i - 1, 1);
}
int left = a[1];
map <int,int> mp;
// for (int i = 1; i <= n; i++) cout << find(i) << ' '; cout << '\n';
// for (int i = 1; i <= n; i++) cout << ch[find(i)] << ' '; cout << '\n';
for (int i = 1; i <= k; i++) {
if (ch[find(i)] == 3) mp[find(i)]++;
else if (ch[find(i)] == 1) {
left--;
}
}
dp[0] = 1;
for (auto [x, y] : mp) {
// cout << y << ' ' << left << '\n';
for (int i = left; i >= y; i--) dp[i] += dp[i - y];
}
cout << dp[left] << '\n';
}
