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<bits/stdc++.h>
using namespace std;
bool DP[31][114514];
int cost[31];
bool prime(int N){
	if(N==0)return false;
	for(int i=2;i*i<=N;i++){
		if(N%i==0)return false;
	}
	return true;
}
int main()
{
	while(true){
		int N,X;
		scanf("%d%d",&N,&X);
		if(N==0&&X==0)return 0;
		for(int i=0;i<N;i++)scanf("%d",&cost[i]);
		for(int i=0;i<=N;i++){
			for(int j=0;j<=X;j++){
				DP[i][j]=false;
			}
		}
		DP[0][0]=true;
		for(int i=1;i<=N;i++){
			for(int j=cost[i-1];j<=X;j++){
				if(DP[i-1][j])DP[i][j]=true;
				if(DP[i-1][j-cost[i-1]])DP[i][j]=true;
				if(DP[i][j-cost[i-1]])DP[i][j]=true;
			}
		}
		bool F=true;
		for(int i=X;i>=1;i--){
			if(F&&DP[N][i]&&prime(i)){
				printf("%d\n",i);
				F=false;
			}
		}
		if(F)printf("NA\n");
	}
}

C++: // AOJ 0202

#include <iostream>
#include <algorithm>

using namespace std;

const int limit = 1000500;

bool prime[limit];
void p(void)
{
	fill(prime, prime + limit, true);
	prime[0] = prime[1] = false;
	for (int i = 2; i * i < limit; i++){
		if (prime[i]){
			for (int j = i * 2; j < limit; j += i){
				prime[j] = false;
			}
		}
	}
	return;
}

int main(void)
{
	p();

	int n, x;
	while (cin >> n >> x, n || x){
		bool dp[limit]; fill(dp, dp + limit, false);
		int hanayo[35];

		for (int i = 0; i < n; i++){
			cin >> hanayo[i];
		}

		for (int i = 0; i < n; i++){
			int kotori = hanayo[i];
			dp[kotori] = true;
			// cout << kotori << " ***** " << endl;
			for (int j = 0; j < limit; j++){
				if (dp[j] && j + kotori <= x){
					// cout << j << " " << kotori << endl;
					dp[j + kotori] = true;
				}
			}
		}

		int ret = -1;
		for (int i = x; i >= 0; i--){
			if (prime[i] && dp[i]){
				ret = i;
				break;
			}
		}
		if (ret == -1){
			cout << "NA" << endl;
		}
		else {
			cout << ret << endl;
		}
	}

	return 0;
}

C++: #include <iostream>

using namespace std;

bool flag[1000001];
int n, x, m, price[30];

bool sosuu(int k) {
	if (k == 2) return true;
	else if (k < 2) return false;
	else if (k % 2 == 0) return false;
	for (int i = 3; i*i<=k; i += 2)
		if (k % i == 0) return false;
	return true;
}
void next(int p, int k) {
	if (flag[k]) return;
	flag[k] = true;
	if (k > x) return;
	if (k > m) if (sosuu(k)) m = k;
	if (p == n) return;
	for (int i = 0; k + price[p] * i <= x; ++i)
		next(p + 1, k + price[p] * i);
}

int main() {
	while (cin >> n >> x, n || x) {
		for (int i = 0; i < 1000001; ++i) flag[i] = false;
		for (int i = 0; i < n; ++i)
			cin >> price[i];
		m = 0;
		next(0, 0);
		if (m) cout << m << endl;
		else cout << "NA" << endl;
	}
}

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

const int Max = 1000001;

int dishes[31];
bool dish[Max];
bool isPrime[Max];

int main(){

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

	int n, x;
	while (std::cin >> n, n){

		std::cin >> x;
		memset(dish, 0, sizeof(dish));

		for (int i = 0; i < n; i++){
			std::cin >> dishes[i];
		}

		dish[0] = true;
		for (int i = 0; i < x; i++){
			if (dish[i]){
				for (int j = 0; j < n; j++){
					if (i + dishes[j] <= Max)dish[i + dishes[j]] = true;
				}
			}
		}

		for (int i = x; i >= 0; i--){
			if (dish[i] && isPrime[i]){
				std::cout << i << std::endl;
				break;
			}
			if (i == 0)std::cout << "NA" << std::endl;
		}
	}

	return 0;
}

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

#ifndef INCLUDE_BOOL_ARRAY_HPP
#define INCLUDE_BOOL_ARRAY_HPP

#include <cstring>
#include <limits>
#include <cassert>

namespace orliv {
template<unsigned int CAP>
struct BoolArray {
  typename int memory_t;
  memory_t K;
  memory_t data[CAP];
  BoolArray() { clear_deep(); }
  void clear_deep(){ std::memset(data, sizeof(data), 0); K = 1; }
  void clear(){ K++; }
  bool within_k(int x, int k){ return data[x] + k >= K; }
  inline bool get(int x){ return data[x] == K; }
  inline void set(int x){ data[x] = K; }
};
}

#endif

using namespace std;

typedef long long ll;
typedef long double ld;
typedef tuple<int, int> duo;
const int dx[] = {0, 0, 1, -1, 1, 1, -1, -1};
const int dy[] = {1, -1, 0, 0, 1, -1, 1, -1};
const int Mod = 1000000000 + 0;
//{{{ templates
#define TT_ template<typename T>inline
#define TTF_ template<typename T,typename F>inline
TT_ T sq(T x){return x*x;}
TT_ T In(){T x;cin>>x;return x;}
TT_ void Out(T&x){cout<<x;}
TT_ void sort(T&v){sort(begin(v),end(v));}
TT_ void revs(T&v){reverse(begin(v),end(v));}
TT_ void uniq(T&v){sort(v);v.erase(unique(begin(v),end(v)),end(v));}
TT_ int ubnd(T&v,typename T::value_type x){return upper_bound(begin(v),end(v),x)-begin(v);}
TT_ int lbnd(T&v,typename T::value_type x){return lower_bound(begin(v),end(v),x)-begin(v);}
TTF_ void inpt(T&v,int n,F f){for(v.reserve(n);n--;v.emplace_back(f()));}
TTF_ void show(T&v,F f,string d=" ",string e="\n"){int i=0;for(auto&x:v)i++&&(cout<<d),f(x);cout<<e;}
TT_ typename T::iterator minel(T&v){return min_element(begin(v),end(v));}
TT_ typename T::iterator maxel(T&v){return max_element(begin(v),end(v));}

inline void fast_io(){ios_base::sync_with_stdio(0);cin.tie(0);}
inline int in(){int x;scanf("%d",&x);return x;}
inline ll pow_mod(ll a,ll k,ll m){ll r=1;for(;k>0;a=a*a%m,k>>=1)if(k&1)r=r*a%m;return r;}
inline ll mod_inv(ll a,ll p){return pow_mod(a,p-2,p);}
//}}} priority_queue queue deque front stringstream max_element min_element insert count make_tuple

const int MAX_N = 10100100;
BoolArray<MAX_N> dp;
bool sieve[MAX_N];

int main()
{
  for (int i = 2; i * i <= MAX_N; i++){
    if (sieve[i]) continue;
    for (int j = i * i; j <= MAX_N; j += i){
      sieve[j] = true;
    }
  }

  int n, x;
  while (n = in(), x = in(), n){
    dp.set(0);
    for (int i = 0; i < n; i++){
      int cost = in();
      for (int j = j + cost <= x; j++){
        if (dp.get(j)) dp.set(j + cost);
      }
    }
    for (int i = x; i > 0; i--){
      if (sieve[i] && dp.get(i)){
        printf("%d\n", i);
        goto END;
      }
    }
    puts("NA");
END:;
    dp.clear();
  }
  return 0;
}