dpgame.cpp

#include<iostream>
#include<vector>

#define long long long
#define nln '\n'

const long MOD = 25071987;

using namespace std;

int main()
{
    cin.tie(0)->sync_with_stdio(0);
    cout.tie(0)->sync_with_stdio(0);
    //freopen("dpgame.inp", "r", stdin);
    long n, k;
    cin >> n >> k;
    vector<bool> crs(n+1, 0);
    for (long i = 1; i <= k; ++i){
        long x;
        cin >> x;
        crs[x] = 1;
    }
    vector<long> f(n+1, 0);
    f[1] = 1;
    for (long i = 2; i <= n; ++i)
        if(!crs[i]){
            f[i] = f[i-1];
            if (i > 2)
                f[i] += f[i-2];
            f[i] %= MOD;
        }
    cout << (f[n] % MOD) << nln;
    return 0;
}