Go: package main

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

var sc = bufio.NewScanner(os.Stdin)

//Sliceconvtoi ...
func Sliceconvtoi() []int {
	strs := strings.Split(sc.Text(), " ")

	var ints []int
	var x int

	for _, s := range strs {
		x, _ = strconv.Atoi(s)
		ints = append(ints, x)
	}

	return ints
}

func isLeapYear(y int) bool {
	return (y%4 == 0 && y%100 > 0) || (y%4 == 0 && y%400 == 0)
}

func cntLeap(y []int) {
	cnt := 0

	for i := y[0]; i <= y[1]; i++ {
		if isLeapYear(i) {
			cnt++
			fmt.Println(i)
		}
	}

	if cnt == 0 {
		fmt.Println("NA")
	}
}

func main() {
	num := 0

	for sc.Scan() {
		y := Sliceconvtoi()

		if y[0] == 0 && y[1] == 0 {
			break
		}

		if num > 0 {
			fmt.Println()
		}

		cntLeap(y)
		num++
	}

}

C++: #include <stdio.h>

void print_na(int a, int b);
void leap_year(int a, int b);

int main(void)
{
    int a, b;
    scanf("%d %d", &a, &b);
    while ( a != 0 || b != 0) {
        print_na(a, b);
        leap_year(a, b);
        printf("\n");
        scanf("%d %d", &a, &b);
    }
    return 0;
}

void print_na(int a, int b)
{
    for (int i = a; i <= b; i++) {
        if ((i % 4 == 0 && !(i % 100 == 0)) || i % 400 == 0) {
            return;
        }
    }
    printf("NA\n");
}

void leap_year(int a, int b)
{
    for (int i = a; i <= b; i++) {
        if ((i % 4 == 0 && !(i % 100 == 0)) || i % 400 == 0) {
            printf("%d\n", i);
        }
    }
}

C++: #pragma GCC optimize ("O3")
#pragma GCC target ("tune=native")
#pragma GCC target ("avx")

#include <bits/stdc++.h>

// 汎用マクロ
#define ALL_OF(x) (x).begin(), (x).end()
#define REP(i,n) for (long long i=0, i##_len=(n); i<i##_len; i++)
#define RANGE(i,is,ie) for (long long i=(is), i##_end=(ie); i<=i##_end; i++)
#define DSRNG(i,is,ie) for (long long i=(is), i##_end=(ie); i>=i##_end; i--)
#define UNIQUE(v) { sort((v).begin(), (v).end()); (v).erase(unique((v).begin(), (v).end()), (v).end()); }
template<class T> bool chmax(T &a, const T &b) {if (a < b) {a = b; return true;} return false; }
template<class T> bool chmin(T &a, const T &b) {if (a > b) {a = b; return true;} return false; }
#define INF 0x7FFFFFFF
#define LINF 0x7FFFFFFFFFFFFFFFLL
#define Yes(q) (q ? "Yes" : "No")
#define YES(q) (q ? "YES" : "NO")
#define DUMP(q) cerr << "[DEBUG] " #q ": " << (q) << " at " __FILE__ ":" << __LINE__ << endl
#define DUMPALL(q) { cerr << "[DEBUG] " #q ": ["; REP(dumpall_i, (q).size()) { cerr << q[dumpall_i] << (dumpall_i == (q).size() - 1 ? "" : ", "); } cerr << "] at " __FILE__ ":" << __LINE__ << endl; }
template<class T> T gcd(const T &a, const T &b) { return a < b ? gcd(b, a) : b ? gcd(b, a % b) : a; }
template<class T> T lcm(const T &a, const T &b) { return a / gcd(a, b) * b; }

// gcc拡張マクロ
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll

// エイリアス
using  ll = long long;
using ull = unsigned long long;
using  ld = long double;
using namespace std;

// モジュール


// 処理内容
int main() {

    bool first = true;

    while (true) {
        
        ll a, b; cin >> a >> b;
        if (!a && !b) break;

        if (!first) cout << "\n";
        first = false;

        bool exist = false;
        RANGE(i, a, b) {
            if (i % 4 == 0 && (i % 100 || i % 400 == 0)) {
                cout << i << endl;
                exist = true;
            }
        }

        if (!exist) {
            cout << "NA\n";
        }

    }
    
}

C++: #include <stdio.h>

int main(void)
{
    int a, b, year answer;
    while(1) {
	scanf("%d %d", &a, &b);
	if (a == 0 && b == 0) {
	    break;
	}
	answer = 0;
	for (year = a; year <= b; year++) {
	    if (year % 4 == 0) {
		if (year % 100 != 0) {
		    printf("%d\n", year);
		    answer++;
		} else if (year % 400 == 0) {
		    printf("%d\n", year);
		    answer++;
		}
	    }
	}
	if (answer == 0) {
   	    printf("NA\n");
	}
	printf("\n");
    }
    return 0;
}

C++: //include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

//math
//-------------------------------------------
template<class T> inline T sqr(T x) {return x*x;}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;
typedef unsigned long long ULL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);

//clear memory
#define CLR(a) memset((a), 0 ,sizeof(a))

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

int main() {
  int a, b;
  VI y;

  cin >> a >> b;
  while(1) {
    for(int i = a; i <= b; i++) {
      if(i % 400 == 0) y.PB(i);
      else if(i % 100 == 0) continue;
      else if(i % 4 == 0) y.PB(i);
    }

    if(y.empty()) cout << "NA" << endl;
    else {
      VI::iterator it = y.begin();
      while(it != y.end()) {
	cout << *it << endl;
	it++;
      }
    }
    y.clear();

    cin >> a >> b;
    if(a+b == 0)break;
    cout << '\n';
  }
}

C++: #include<iostream>
#include<cstdio>
using namespace std;

int main(){
  int a,b,k=0,i,j=0;
  
  while(1){
    cin>>a>>b;
    if(a==0&&b==0)break;
   
    if(j) cout<<endl;
    k=0;
    for(i=a;i<=b;i++){
      if(i%4==0&&i%100!=0){cout<<i<<endl;k++;}
      if(i%400==0){cout<<i<<endl;k++;}
    }    
    if(k==0)cout<<"NA"<<endl;
    j=1;  
  }
return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <functional>
#include <numeric>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <utility>
#include <sstream>
#include <complex>

using namespace std;

#define FOR(i,a,b) for(long long i=(a);i<(b);i++)
#define REP(i,N) for(long long i=0;i<(N);i++)
#define ALL(s) (s).begin(),(s).end()
#define fi first
#define se second

#define PI acos(-1.0)
#define INF 1000000007

typedef long long ll;
typedef pair<ll, ll> P;
typedef pair<double, double> PD;
typedef pair<string, ll> PS;
typedef vector<ll> V;

int a, b;
V vi;

int main(){
	while (cin >> a >> b&&a+b){
		for (int i = a; i <= b; i++){
			if (i % 4 == 0){
				if (i % 100 == 0){
					if (i % 400 == 0){
						vi.push_back(i);
					}
					continue;
				}
				vi.push_back(i);
			}
		}
		if (vi.empty())cout << "NA" << endl;
		REP(i, vi.size()){
			cout << vi[i] << endl;
		}
		vi.clear();
	}
}

C++: #include<iostream>
int main(){for(int a,b,c;std::cin>>a>>b,a||b;){c=0;for(;a<=b;a++)if(!(a%400)||!(a%4)&&(a%100))c++,std::cout<<a<<'\n';if(!c)std::cout<<"NA\n";std::cout<<'\n';}}