二进制枚举

#include<bits/stdc++.h>
using namespace std;
int n,k,a[78],ans;
bool zs(int x){
	if(x<2)return 0;
    if(x==2)return 1;
    if(x%2==0)return 0;
	for(int i=2;i*i<=x;i++){
		if(x%i==0)return 0;
	}
	return 1;
}
void dfs(int d,int s,int c){//2进制枚举
    if(d==n+1){
        if(zs(s)&&c==k){
            ans++;
        }
        return;
    }
    dfs(d+1,s,c);//0
    dfs(d+1,s+a[d],c+1);//1
}
int main(){
    cin>>n>>k;
    for(int i=1;i<=n;i++)cin>>a[i];
    dfs(1,0,0);
    cout<<ans;
	return 0;
}