#include<iostream>
using namespace std;

int fibo (int n){
    if(n==0 ||n==1){
      return 1;
    }else if (n==2){
      return 2;
    }else{
      return fibo(n-1) + fibo(n-2);
    }
}
  
int main(){
  int n,m, answer=1;
  cin >> n >> m;
  int a[n];
  cin >> a[0];
  for(int i= 1; i<m; i++){
    cin >> a[i];
    if (a[i]-a[i-1] ==1){
      answer= 0;
      break;
    }else{
      answer *= fibo(a[i] - a[i-1] -1);
  }
  
  
  cout << answer;
  return 0;
}  