1979 第K个数

#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
#define N 10010
int n,k,a[N];
bool judge(int x){
    if(x<2) return 0;
    for(int i=2;i<=sqrt(x);i++) if(x%i==0) return 0;
    return 1;
}
int main(){
    scanf("%d%d",&n,&k);
    int t=n-k+1;
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    nth_element(a+1,a+k,a+n+1);
    int kx=a[k];
    nth_element(a+1,a+t,a+n+1);
    int kd=a[t];
    int ans=kd-kx;
    puts(judge(ans)?"YES":"NO");
    printf("%d\n",ans);
    return 0;
}