Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
	"fmt"
	)

var scanner = bufio.NewScanner(os.Stdin)

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		x, _ := strconv.Atoi(buf[1])
		prime_table := make([]int, 1000001)
		prime_table[0] = -1
		prime_table[1] = -1
		for i := 2; i < 1000001; i++ {
			if prime_table[i] != -1 {
				prime_table[i] = 1
				for j := 2*i; j < 1000001; j += i {
					prime_table[j] = -1 // -1 means "not prime"
				}
			}
		}
		dp := make([]int, x+1)
		dp[0] = 1
		menu := make([]int, n)
		for i := 0; i < n; i++ {
			scanner.Scan()
			menu[i], _ = strconv.Atoi(scanner.Text())
		}
		for i := 0; i < n; i++ {
			for j := 0; j <= x; j++ {
				if menu[i] <= j && dp[j-menu[i]] != 0 {
					// log.Println(dp)
					dp[j] = 1
				}
			}
		}
		flag := true
		for j := x; j >= 0; j-- {
			if prime_table[j] == 1 && dp[j] == 1 {
				flag = false
				fmt.Println(j)
				break
			}
		}
		if flag {
			fmt.Println("NA")
		}
	}
}

C++: #include <iostream>
#include <algorithm>
#include <limits>
#include <cstring>

constexpr int MAX_X = 1000001;
constexpr int MAX_N = 31;

int n, x, values[MAX_N];
bool is_prime_number[MAX_X] = {true};

void initialize();

void solve();

int main(){
    initialize();
    while(true){
        memset(values, 0, MAX_N);

        std::cin >> n >> x;
        
        if(n + x == 0) break;
        
        for(int i = 0; i < n; ++i)
            std::cin >> values[i];

        solve();
    }
}

void initialize(){
    is_prime_number[0] = false, is_prime_number[1] = false;
    for(int i = 2; i * i <= MAX_X; ++i){
        if(is_prime_number[i]){
            for(int j = i + 1; j < MAX_X; ++j){
                if(j % i == 0)
                    is_prime_number[j] = false;
            }
        }
    }
}

void solve(){
    int ans = 0;
    int dp[MAX_X];
    memset(dp, 0, MAX_X);

    /*
    std::cout << "x : " << x << std::endl << "n : " << n << std::endl;
    for(int i = 0; i < (x > 1000 ? 1000 : x); ++i){
        std::cout << i << " dp : " << dp[i] << std::endl;
    }
    */

    for(int i = 1; i <= x; ++i){
        int res = 0;
        for(int j = 0; j < n; ++j){
            if(values[j] <= i){
                res = std::max(dp[i - values[j]] + values[j], res);
            }
        }
        dp[i] = std::max(dp[i], res);
        if(is_prime_number[dp[i]]){
            ans = std::max(dp[i], ans);
        }
    }

    if(ans != 0){
        std::cout << ans << std::endl;
    }
    else{
        std::cout << "NA" << std::endl;
    }

}

C++: #include<iostream>
#include<string>
#include<cstdio>
#include<algorithm>
#include<stack>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
#include<set>
#include<complex>
#define vi vector<int>
#define vvi vector<vector<int> >
#define ll long long int
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vc vector<char>
#define vs vector<string>
#define ld long double
#define INF 1e9
#define EPS 0.0000000001
#define rep(i,n) for(int i=0;i<n;i++)
#define CC puts("-------ok--------");
#define all(in) in.begin(), in.end()
#define bv vector<bool>
using namespace std;
typedef pair<int, int> PI;
#define MAX 1000009
ll m=0; int n=0; int ans=0;
bool flag;
vi v;
vb memo(MAX+10,true);
/*void dfs(int num){
    if(flag) return;
    if(ans==num){flag=true;return;}
    if(num>ans){memo[num]=false;return;}
    else rep(i,n){
        cout<<num<<endl;
      if(num+v[i]<=ans&&memo[num+v[i]])dfs(num+v[i]);
    }
    memo[num]=false;
    return;
}*/
int main(){
    vector<bool>check(MAX+1);  //index number will be checked
    rep(i, MAX+1)check[i] = true;
    vector<int>Primenumber(MAX+1,0); //Primearray
    int counter =0;                  //Primearray counter;
    for(int i = 2; i<MAX+1;i++){
        if(check[i]){
            for(int j = 2;i*j<MAX;j++)
                check[i*j] = false;//?´???°??????Primearray???????´??????????????????°?????¨???false???
            Primenumber[counter] = i;
            counter++;
        }
    }
    while(cin>>n>>m,n+m){
        int temp;
        flag=false;
        rep(i,n){cin>>temp; v.push_back(temp);}
        for(int i=(int)m;i>=0;i--){
            if(check[i]){
                ans=i;break;}
        }
        bool array[1000000]={false};
        rep(i,n)array[v[i]]=true;
        for(int i=1;i<=ans;i++) {
            if(array[i])rep(j,n)if(i+v[j]<=ans)array[i+v[j]]=true;
        }
        flag=array[ans];
        if(flag) cout<<ans<<endl;
        else cout<<"NA"<<endl;
        v.clear();
    }
}

C++: #include<stdio.h>
int hideo[1000001] = { 0 };
int noyori = 0, debu = 0, n, x, temp = 1;
int main(void)
{
	int  ruio[31] = { 0 };
	while (scanf("%d %d", &n, &x)) {
		if (n == 0 && x == 0) {
			return 0;
		}
		for (int i = 1; i <= n; i++) {
			scanf("%d", &ruio[i]);
			hideo[ruio[i]] = 1;
		}
		while (temp != x) {
			if (hideo[temp] == 1) {
				for (int j = 1; j <= n; j++) {
					if (temp + ruio[j] > x)continue;
					if (hideo[temp + ruio[j]] == 0) {
						hideo[temp + ruio[j]] = 1;
					}
				}
			}
			temp++;
		}
		for (int i = x; i >= 1; i--) {
			if (hideo[i] == 1) {
				for (int j = 2; j < i - 1; j++) {
					if (i%j == 0) {
						debu=1;
					}
				}
				if (debu == 0) {
					noyori = i;
					break;
				}
			}
			debu = 0;
		}
		if (noyori > 1 ) {
			printf("%d\n", noyori);
		}
		else {
			printf("NA\n");
		}
		temp = 1;
		noyori = 0;
		debu = 0;
		for (int i = 1; i <= n; i++) {
			ruio[i] = 0;
		}
		for (int i = 1; i <= x; i++) {
			hideo[i] = 0;
		}
	}
	return 0;
}