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

#ifdef genshin
#include <experimental/iterator>
#endif
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using uint = unsigned int;
const double EPS = 1e-8;
const int INF = 0x3F3F3F3F;
const ll LINF = 46 * ll(1e17);
const int MOD = 1e9 + 7;
const int maxn = 1e5 + 25;


int dp[5050], s[5050];
signed main() { ios::sync_with_stdio(0); cin.tie(0);
    int n, m;

    cin >> n >> m;
    dp[0] = 1;
    int l = 1, mn = n+1, mx = 0;
    for (int i=1;i<=n;++i){
        cin >> s[i];
        mn = min(mn, s[i]);
        mx = max(mx, s[i]);
        if (mn == l && mx == i){
            int fs = s[l], ss = -1, cnt = 1;
            for (int j=l+1;j<=i;++j){
                if (s[j] == fs + 1) ++fs, ++cnt;
                else if (s[j] == ss + 1) ++ss;
                else if (s[j] == l) ss = l;
                else{
                    cout << "0\n";
                    return 0;
                }
            }
            int tr1 = cnt, tr2 = i - l + 1 - cnt;
            if (tr1 > tr2) swap(tr1, tr2);

            for (int j=n;j>=tr2;--j){
                dp[j] = (dp[j - tr1] + dp[j - tr2]) % MOD;
            }
            for (int j=tr2-1;j>=tr1;--j){
                dp[j] = dp[j - tr1];
            }
            for (int j=tr1-1;j>=0;--j){
                dp[j] = 0;
            }

            l = i+1;
            mn = n+1;
            mx = 0;
        }
    }
    int ans = 0;
    for (int i = n-m;i<=m;++i) ans = (ans + dp[i]) % MOD;
    cout << ans << '\n';
}