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 leap_year(int a, int b);

int main(void)
{
    while (1){
        int a, b;
        scanf("%d %d", &a, &b);
        if (a == 0 && b ==0) {
            break;
        } else {
            leap_year(a, b);
        }
    }
    return 0;
}

void leap_year(int a, int b)
{
    int count = 0;
    for(int i = a; i <= b; i++){
        int j = i;
        if (i - j / 400 * 400 == 0) { //iが４００の倍数の時
            printf("%d\n", i);
            count = + 1;
            j = i;
        } else if (!(i - j / 100 * 100 == 0)) { //iが100の倍数のでないとき
            int j = i;  
            if ( i - j / 4 * 4 == 0) {//iが四の倍数のとき
                printf("%d\n", i);
                count = + 1;                
            }
        }
    }
    if (count == 0) { //閏年が0のとき
        printf("NA");
    }    
}

C++: #include <iostream>
  
bool ifEndValInput(int input_n1, int input_n2);
bool inputValRangeCheck(int input_n1, int input_n2);
void printLeapYear(int start_y, int end_y);
bool isLeapYear(int year);
   
   
int main()
{
    int start_year, end_year;
    while (true) {
        std::cin >> start_year >> end_year;
        if (ifEndValInput(start_year, end_year)) {
            break;
        }
        if (inputValRangeCheck(start_year, end_year)) {
            printLeapYear(start_year, end_year);
        }
        std::cout << std::endl;
    }
    return 0;
}
  
bool ifEndValInput(int input_n1, int input_n2)
{
    if (input_n1 == 0 && input_n2 == 0) {
        return true;
    }
    return false;
}
  
bool inputValRangeCheck(int input_n1, int input_n2)
{
    if (input_n1 <= 0 || input_n1 > input_n2 || input_n2 >= 1000) {
        return false;
    }
    return true;
}
   
   
bool isLeapYear(int year)
{
    if (year % 400 == 0) {
        return true;
    } else if (year % 100 == 0) {
        return false;
    } else if (year % 4 == 0) {
        return true;
    } else {
        return false;
    }
}
   
void printLeapYear(int start_y, int end_y)
{
    bool does_leap_year_exist = false;
    for (int i = start_y; i <= end_y; i++) {
        if (isLeapYear(i) == true) {
            std::cout << i << std::endl;
            does_leap_year_exist = true;
        }
    }
    if (!does_leap_year_exist) {
        std::cout << "NA" << std::endl;
    }
}

C++: #include<stdio.h>
    
int leap_year(int x);
        
int main(void)
{
    int start_year, end_year, counter;
    while(1){
        scanf("%d %d", &start_year, &end_year);
        if(start_year == 0 && end_year == 0){
            break;
        }else{
            counter = 0;
            for(int i = start_year; i <= end_year; i++){
                counter += leap_year(i); 
                }
            if( counter == 0){
                printf("NA\n");
            } 
            printf("\n");
        }
    }
    return 0;
}
    
    
int leap_year(int x)
{
    if((x % 4 == 0 && !(x % 100 == 0)) || x % 400 == 0){
        printf("%d\n", x);
        return 1;
    }
    return 0;
}

C++: #include <stdio.h>
#include <stdbool.h>

bool is_leap_year(int y);
int get_leap_years(int* leap_years_list, int year_begin, int year_end);


int main()
{
    int leap_years_list[1000]; //A.D. 0 - A.D. 3000 の間に閏年は高々1000個しかない

    bool first_set = true; //一つ目のセットの前にだけは改行を入れてはいけないので

    while (true) {
        int year_begin, year_end;

        //読み込み
        scanf("%d %d", &year_begin, &year_end);

        //終了判定
        if (year_begin == 0 && year_end == 0) {
            break;
        }

        //閏年を計算する
        int leap_years_count = get_leap_years(leap_years_list, year_begin, year_end);

        //セットとセットの間には空行を入れる
        if (first_set) {
            first_set = false;
        } else {
            putchar('\n'); //putcharは一文字だけ出力する関数です
        }

        //閏年を出力
        if (leap_years_count == 0) {
            puts("NA"); //putsは与えられた文字列を出力した後改行する関数です
        } else {
            for (int i = 0; i < leap_years_count; i++) {
                printf("%d\n", leap_years_list[i]);
            }
        }
        
    }
}

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

int get_leap_years(int* leap_years_list, int year_begin, int year_end)
{
    int year;
    int i = 0;
    for (year = year_begin; year <= year_end; ++year){
        if (is_leap_year(year) == true) {
        *(leap_years_list + i) = year;
        ++i;
        }
    }
    return i;
}

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

bool isLeapYear(int year){
	if (year % 400 == 0)
		return true;
	if (year % 4 == 0){
		if (year % 100 == 0)
			return false;
		else
			return true;
	}
	return false;
}

int main(){
	int a, b, count;
	int n = 0;

	while (true){
		cin >> a >> b;
		if (a == 0 && b == 0)break;
		if (n != 0)cout << endl;

		count = 0;
		for (int i = a; i <= b; ++i){
			if (isLeapYear(i)){
				++count;
				cout << i << endl;
			}
		}
		if (count == 0)
			cout << "NA" << endl;
		++n;

	}



	return 0;
}

C++: #include<stdio.h>
    
int leap_year(int x);
        
int main(void)
{
    int start_year, end_year, counter;
    while(1){
        scanf("%d %d", &start_year, &end_year);
        if(start_year == 0 && end_year == 0){
            break;
        }else{
            counter = 0;
            for(int i = start_year; i <= end_year; i++){
                counter += leap_year(i); 
                }
            if( counter == 0){
                printf("NA\n");
            }
        }
    }
    return 0;
}
    
    
int leap_year(int x)
{
    if((x % 4 == 0 && !(x % 100 == 0)) || x % 400 == 0){
        printf("%d\n", x);
        return 1;
    }
    return 0;
}

C++: #include<iostream>

using namespace std;

int main() {
	int a[3000], b[3000],n=0;
	while(1){
		cin >> a[n] >> b[n];
	if (a[n] == 0 && b[n] == 0)break;
		n++;
	}
	for(int j=0;j<=n;j++){
		if (a[j] == 0 && b[j] == 0)break;
		int cnt = 0;
		if (j != 0)cout << endl;
		for (int i = a[j]; i <= b[j]; i++) {
			
			
			if (i % 4 == 0) {
				if (i % 100 == 0) {
					if (i % 400 == 0) {
						cnt++;
						cout << i << endl;
					}
				}
				else {
					cnt++;
					cout << i << endl;
				}
			}
			if (i == b[j]) {
				if (cnt == 0)cout << "NA" << endl;
			}
		}
	}
	return 0;
}

C++: #include <iostream>

int main() {
    int a, b, n = 0, m = 0;
    std::cin >> a >> b;
    while (a != 0 && b != 0) {
        if(m >= 1){
        std::cout << std::endl;
        }
        for (int i = a; i <= b; ++i) {
            if (i % 400 == 0) {
                std::cout << i << std::endl;
                n = 1;
            } else if (i % 100 != 0 && i % 4 == 0) {
                std::cout << i << std::endl;
                n = 1;
            } else  {
                continue;
            }
        }
        if (n == 0) {
            std::cout << "NA" << std::endl;
        }
        std::cin >> a >> b;
        n = 0;
        m++;
    }
    return 0;
}