哪错了？？？

#include<bits/stdc++.h>
using namespace std;
int a,b,c[21],k=0;
int m(int m1){
    if(m1<=1)return 0;
    if(m1==2||m1==3)return 1;
    if(m1%2==0)return 0;
    int m2=sqrt(m1);
    for(int i=3;i<=m2;i+=2)if(m1%i==0)return 0;
    return 1;
}
int f(int f1,int f2,int f3){
    if(f1==b)k+=m(f2);
    for(int i=f3;i<a-(b-f1);i++)f(f1+1,f2+c[i],f3+1);
    return 0;
}
int main(){
    cin>>a>>b;
    for(int i=0;i<a;i++)cin>>c[i];
    f(0,0,0);
    cout<<k;
    return 0;
}