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 <cmath>
#include <iostream>

#define rep(i, n) for (int i = 0; i < n; i++)

bool is_prime(int n) {
    if (n % 2 == 0) return false;
    for (int i = 3; i <= std::sqrt(n); i += 2)
        if (n % i == 0) return false;
    return true;
}

int main() {
    int n, x;
    while (std::cin >> n >> x && n > 0 && x > 0) {
        bool course[x + 1];
        rep(i, x + 1) course[i] = false;

        int prices[n];
        rep(i, n) {
            std::cin >> prices[i];
            course[prices[i]] = true;
        }
        course[0] = true;

        int max = -1;
        rep(i, x + 1) rep(j, n) {
            if (i - prices[j] >= 0 && course[i - prices[j]]) {
                if (is_prime(i)) max = i;
                course[i] = true;
                std::cout << i << ' ';
                break;
            }
        }
        std::cout << std::endl;
        if (max < 0)
            std::cout << "NA" << std::endl;
        else
            std::cout << max << 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;
/*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){
        vi v;
        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[MAX]; rep(i,MAX)array[i]=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;
            if(array[ans])break;
        }
        flag=array[ans];
        if(flag) cout<<ans<<endl;
        else cout<<"NA"<<endl;
    }
}

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

constexpr int MAX_X = 1000000, MAX_N = 30;

int value[MAX_N], dp[MAX_X + 1], n, x;
bool is_prime_number[MAX_X + 1];

void initialize();

void solve();

int main(){
    initialize();

    while(true){
        std::cin >> n >> x;
        if(n == 0 && x == 0){
            break;
        }
        
        for(int i = 0; i < n; ++i){
            std::cin >> value[i];
        }

        solve();
    }
    return 0;
}

void solve(){
    int ans = 0;

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

            dp[i] = std::max(dp[i], res);

            if(is_prime_number[dp[i]]){
                ans = std::max(ans, dp[i]);
            }
        }
    }

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

void initialize(){
    memset(is_prime_number, true, MAX_X + 1);

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

C++: #include <bits/stdc++.h>

const int MOD = 1e9 + 7;
const int iINF = 1000000000;
const long long int llINF = 1000000000000000000;
const double PI = acos(-1.0);
#define rep(i, n) for (int i = 0; i < (n); i++)

using namespace std;
using ll = long long int;
using P = pair<int, int>;
using T = tuple<int, int, int>;
using edge = struct
{
    int to;
    int cost;
};

int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

bool isPrime[1000010];
bool dp[1000010];

void Eratostenes(int N)
{
    rep(i, 1e6 + 1) isPrime[i] = true;

    isPrime[0] = false;
    isPrime[1] = false;

    for(int i = 2; i <= sqrt(N); i++)
    {
        if(isPrime[i])
        {
            for(int j = i * 2; j <= N; j += i)
                isPrime[j] = false;
        }
    }   
}

int main()
{
    int N, X;
    Eratostenes(1000000);   

    while(cin >> N >> X && N)
    {
        vector<int> v(N);
        rep(i, N) cin >> v[i];

        dp[0] = true;

        rep(i, N)
        {
            rep(j, X + 1)
            {
                if(!dp[j]) continue;

                dp[j + v[i]] = true;
            }
        }

        int ans = 0;

        rep(i, X + 1)
        {
            if(dp[i] && isPrime[i])
                ans = max(ans, i);
        }

        cout << (ans == 0 ? "NA" : to_string(ans)) << endl;

    }

    return 0;
}