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])
		if n == 0 && x == 0 {
			break
		}
		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 <bits/stdc++.h>
using namespace std;
#define FOR(i, s, n) for(int i = s; i < (int)n; i++)
#define per(i, n) for(int i = n; i >= 0; i--)
#define ROF(i, s, n) for(int i = s; i >= (int)n; i--)
#define FORIT(i, A) for (auto i : A)
#define PRINT(x) cout << (x) << "\n"
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define MP make_pair
#define EACH(i, n) for (__typeof((n).begin()) i = (n).begin(); i != (n).end(); ++i)
#define SZ(a) int((a).size())
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define CLR(a) memset((a), 0 ,sizeof(a))
#define dump(x) cout << #x << " = " << (x) << "\n";
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << "\n";
#define sq(n) (n) * (n)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef vector<LL> VLL;
typedef vector<VLL> VVLL;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef priority_queue<int> maxpq;
typedef priority_queue< int, vector<int>, greater<int> > minpq;
static const double EPS = 1e-10;
static const double PI = acos( -1.0 );
static const int mod = 10007;
static const int INF = 1 << 25;
static const LL LL_INF = 1152921504606846976;
static const int dx[] = { -1, 0, 1, 0,  1, -1,  1, -1 };
static const int dy[] = { 0, -1, 0, 1 , 1,  1, -1, -1 };

static bool is_pm[ 10000001 ];
static bool dp[ 10000001 ];
static ull ans = 0, m;
static char n;
static ull ar[ 30 ];

static void solve( const ull how_much ) {
	if ( how_much > m  ) {
		return;
	}
	if ( is_pm[ how_much ] ) {
		ans = max( ans, how_much );
	}
	if ( how_much == m ) {
		return;
	}
	if ( dp[ how_much ] ) {
		return;
	}
	
	dp[ how_much ] = true;
	for ( int i = 0; i < n; i++ ) {
		solve( how_much + ar[ i ] );
	}
}

int main() {
	memset( is_pm, -1, sizeof( is_pm ) );
	for ( ull i = 2; i * i <= 10000000; i += 2 ) {
		if ( is_pm[ i ] ) {
			for ( ull j = i * i; j <= 10000000; j += i) {
				is_pm[ j ] = false;
				if ( i % 2 == 1 ) {
					j += i;
				}
			}
		}
		if ( i == 2 ) {
			--i;
		}
	}
	while ( ~scanf( "%d %d", &n, &m ) && n && m ) {
		for ( int i = 0; i < n; i++ ) {
			scanf( "%d", &ar[ i ] );
		}
		sort( ar, ar + n );
		reverse( ar, ar + n );
		memset( dp, false, sizeof( dp ) );
		ans = 0;
		solve( 0 );
		if ( ans == 0 ) {
			printf( "NA\n" );
		}
		else {
			printf( "%d\n", ans );
		}
	}
	return 0;
}

C++: #include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <complex>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <functional>
#include <iostream>
#include <map>
#include <set>
using namespace std;
typedef pair<int,int> P;
#define pu push
#define pb push_back
#define mp make_pair
#define eps 1e-7
#define INF 2000000000
#define EQ(a,b) (abs((a)-(b))<EPS)
#define rep(i,j) for(int i=0;i<j;i++)
#define repi(i,j,k) for(int i=j;i<k;i++)
#define Max_N 1000010
bool prime[Max_N];
int menu[30];
bool dp[Max_N];
void eratos()
{
	repi(i,2,Max_N)prime[i]=true;
	prime[0]=false;
	prime[1]=false;
	for(int i=2;i*i<=Max_N;i++)
	{
		if(prime[i])
		{
			for(int j=2*i;j<Max_N;j+=i)
			{
				prime[j]=false;
			}
		}
	}
	return;
}
int main()
{
	rep(i,Max_N)dp[i]=false;
	eratos();
	while(1)
	{
		int n,x;
		cin >> n >> x;
		if(n==0&&x==0)break;
		for(int i=0;i<n;i++)
		{
			cin >> menu[i];
		}
		dp[0]=true;
		int ans=0;
		for(int i=1;i<=x;i++)
		{
			for(int j=0;j<n;j++)
			{
				if(i-menu[j]>=0&&dp[i-menu[j]])
				{
					dp[i]=true;
                                        break;
				}
			}
			if(prime[i]&&dp[i])
			{
				ans=i;
			}	
		}
		if(ans!=0)
		{
			cout << ans << endl;
		}
		else
		{
			cout << "NA" << endl;
		}
	}
	return 0;
}

C++: #include<iostream>
#include<bitset>
#include<algorithm>
using namespace std;
int n,x;
bool isp[1<<20];
main()
{
	isp[0]=isp[1]=1;
	for(int i=2;i<1<<20;i++)
	{
		if(isp[i])continue;
		for(int j=i+i;j<1<<20;j+=i)isp[j]=1;
	}
	while(cin>>n>>x,x)
	{
		bitset<1000001>dp;
		dp[0]=1;
		for(int i=0;i<n;i++)
		{
			int v;cin>>v;
			for(int j=0;(v<<j)<=x;j++)dp|=dp<<(v<<j);
		}
		bool f=1;
		for(int i=x;i>0;i--)
		{
			if(!dp[i])continue;
			if(!isp[i])
			{
				cout<<i<<endl;
				f=0;
				break;
			}
		}
		if(f)cout<<"NA"<<endl;
	}
}