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 <iostream>
#include <fstream>
#include <typeinfo>
#include <vector>
#include <cmath>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <cstdio>
#include <queue>
#include <iomanip>
#include <cctype>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<25;
const double pi=acos(-1);
const double eps=1e-8;
const vi emp;

int a,b;

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

C++: #include<stdio.h>
/*与えられた期間の間のうるう年をすべて出力*/
void leap_year(int year1, int year2);

int main(void)
{
    while(1){
        int a, b; /*a は year1　, b は year2*/
        scanf("%d %d", &a, &b);
        if (a == 0 && b == 0){
            break;
        }else if (a == b){
            printf("NA\n");
            printf("\n");
        }else{
            leap_year(a, b);
        }
    }
    return 0;
}

void leap_year(int year1, int year2)
{
    for(int i = year1; i <= year2; ++i){
        if ((i % 4 == 0 && i % 100 != 0) || i % 400 == 0){
            printf("%d\n", i);
        }
    }    
    printf("\n");
}

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

bool isLeap(int y){
  if(y%400==0)return true;
  if(y%100==0)return false;
  if(y%4==0)return true;
  return false;
}

int main(){
  int a,b;
  bool line=false;
  while(cin >> a >> b, a||b){
    if(line)cout << endl;
    line = true;

    bool f=false;
    for(int i=a;i<=b;i++)
      if(isLeap(i)){
	cout << i << endl;
	f=true;
      }
    if(!f)cout << "NA\n";
  }
}

C++: #include <iostream>
#include <algorithm>
#include <vector>
#include <cstdio>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cmath>
#include <functional>
#include <numeric>
#include <iomanip>
#define fi first
#define se second
#define fcout(n) cout<<fixed<<setprecision((n))
#define cinl(str) getline(cin,(str))
using namespace std;
bool value(int y,int x,int R,int C){return 0<=y&&y<R&&0<=x&&x<C;}
typedef pair<int,int> pii;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long > vll;
typedef vector< vi > vvi;
double pie=acos(-1);
int INF=10000009;
int dx[4] = { 0,-1,0,1 };
int dy[4] = { -1,0,1,0 };
int main() {
	int a,b;
	int x=0;
	while(true){
		cin>>a>>b;
		if(a+b==0) break;
		for(int i=a;i<=b;i++){
			if((i%4==0&&i%100!=0)||i%400==0){
				cout<<i<<endl;
				x++;
			}
			if(i==b&&x==0){
				cout<<"NA"<<endl;
			}
		}
		x=0;
	}
}

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) {
        printf("\n");
        print_na(a, b);
        leap_year(a, b);
        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++: #include <iostream>

int LeapYear (int x);
int main()
{
    int a,b;
    std::cin >> a >> b;
    while (true) {
        int n = 0;
        if (a == 0 && b == 0) {
	        break;
        } else {
            for (int i = a; i <= b; i++) {
                if (LeapYear (i) == 1) {
                    std::cout << i << std::endl;
                    n++;
            }				
        }
        if (n == 0) {
            std::cout << "NA" << std::endl;
        }
        std::cin >> a >> b;
        }
    }
    return 0;
}

int LeapYear (int x)
{
    if (x % 400 == 0) {
    return 1;
    } else if (x % 100 == 0) {
    return 0;
    } else if (x % 4 == 0) {
    return 1;
    }else {
    return 0;
    }
}

C++: #include<stdio.h>
#include <algorithm>
#include <cassert>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <iostream>
#include <iterator>
#include <list>
#include <map>     
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <iomanip>
#include <stack>
#include <string>
#include <vector>
using namespace std;
#define ll long long
#define ld long double
#define rep(a,t) for(int a=0;a<t;a++) 
#define forever while(true)
#define Sort(a) sort(a.begin(),a.end())
#define Reverse(a) reverse(a.begin(),a.end())
#define pb push_back
int main()
{
	cin.tie(0);
	ios::sync_with_stdio(false);
	bool leap[3001];
	for (int i = 0; i < 3001; i++) {
		int y = i;
		if (y % 4 != 0) { leap[i] = false; }
		else if(y%100!=0){
			leap[i] = true;
		}
		else if (y % 400 != 0) {
			leap[i] = false;
		}
		else {
			leap[i] = true;
		}
	}
	int a, b;
	bool first = true;
	while (cin >> a >> b) {
		bool ever = false;
		if (a == 0 && b == 0) { break; }
		if (!first) { cout << endl; }
		for (int i = a; i <= b; i++) {
			if (leap[i]) { ever = true; cout << i << endl; }
		}
		if (!ever)
		{
			cout << "NA" << endl;
		}first = false;
	}
	return 0;
}

C++: #define _CRT_SECURE_NO_WARNINGS
#include "bits/stdc++.h"
using namespace std;

int main(int argc, char ** argv) {
    int a, b;
    for (int q = 0;; q++){
        scanf("%d%d", &a, &b);
        if (a == 0) break;
        if (q != 0) puts("");
        auto is_uruu = [](int y){
            if (y % 400 == 0) return true;
            return y % 4 == 0 && y % 100 != 0;
        };
        int na = true;
        for (int i = a; i <= b; i++){
            if (is_uruu(i)){
                na = false;
                printf("%d\n", i);
            }
        }
        if (na) puts("NA");
    }
}

C++: #include<stdio.h>
/*与えられた期間の間のうるう年をすべて出力*/
void leap_year(int year1, int year2);

int main(void)
{
    while(1){
        int a, b; /*a は year1　, b は year2*/
        scanf("%d %d", &a, &b);
        if (a == 0 && b == 0){
            break;
        }else if (a == b){
            printf("NA\n");
            printf("\n");
        }else {
            leap_year(a, b);
        }
    }
    return 0;
}

void leap_year(int year1, int year2)
{   
    int limit = 0; /*もしも、うるう年がなかった時に使う*/
    for(int i = year1; i <= year2; ++i){
        if ((i % 4 == 0 && i % 100 != 0) || i % 400 == 0){
            printf("%d\n", i);
        }else{
            ++limit;
        }
    }
    if (limit == (year2 - year1 + 1)){/*うるう年がない場合*/
        printf("NA\n");
        printf("\n");
    }else{    /*うるう年がある場合*/
    printf("\n");
    }
}