C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<iomanip>
#include<cstdlib>
#include<algorithm>
#include<cmath>
using namespace std;
int n,k,x[1001],ans=0;
bool prime(int a){
	if(a==0||a==1) return 0;
	if(a==2) return 1;
	if(a%2==0) return 0;
	for(int i=3;i<=sqrt(a);i+=2) if(a%i==0) return 0;
	return 1;
}
void dnf(int e,int tot,int k1){
	if(e==k) {
		if(prime(tot)) ans++;
		return;
	}
	for(int i=k1;i<n-k+e+2;i++) {
		dnf(e+1,tot+x[i],i+1);
	}
}
int main(){
	int i,j;
	//freopen("num.in","r",stdin);
	//freopen("num.out","w",stdout);
	scanf("%d%d",&n,&k);
	for(i=1;i<=n;i++) scanf("%d",&x[i]);
	dnf(0,0,1);
	printf("%d\n",ans);
	return 0;
}