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>
#include <stdbool.h>

bool is_leap_year(int y);

int get_leap_years(int leap_years_list[1000], int year_begin, int year_end)
{
    int count = 0;
    while(int year = year_begin; year <= year_end; ++year) {
        if (is_leap_year(year) != false) {
            leap_years_list[count] = year;
            ++count;
        }
    }
    return count;
}
        

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;
    }
}

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

int main(){
	int year[3001];
	for(int i=0;i<3001;i++){
		if(i%4==0){
			year[i]=1;
		}else year[i]=0;
		if(i%100==0){
			year[i]=0;
		}
		if(i%400==0){
			year[i]=1;
		}
	}
	int a,b;
	cin>>a>>b;
	int cnt=0;
	if(a==0 && b==0)goto LABEL;
	for(int j=a;j<=b;j++){
		if(year[j]==1){
			cout<<j<<endl;
			cnt++;
		}
	}
	if(cnt==0)cout<<"NA"<<endl;
	while(1){
		cin>>a>>b;
		if(a==0 && b==0){
			break;
		}else{cout<<endl;}
		for(int j=a;j<=b;j++){
			if(year[j]==1){
				cout<<j<<endl;
				cnt++;
			}
		}
		if(cnt==0)cout<<"NA"<<endl;
	}
	LABEL:
	return 0;
}

C++: #include <stdio.h>

int hantei(int year);
//???????????´????????????????????????????????????

int main(void)
{
	int year[2];
	int NA;
	for(;;) {
		scanf("%d %d", &year[0], &year[1]);
		if(year[0] == 0 && year[1] == 0) {
			break;
		}
		NA = 0;
		for(int i = year[0]; i <= year[1]; i++) {
			if(hantei(i) == 1) {
			printf("%d\n", i);
			NA++;
			}
		}
		if(NA == 0) {
			printf("NA\n\n");
		}else{
		    printf("\n");
                }
	}
	return 0;
}

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

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 >= 3000) {
        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)) {
            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 main(void)
{
	int i,a,b,w,x,flg,cnt;
	cnt=0;
	scanf("%d %d",&a,&b);
	while(a!=0 && b!=0){
		flg=0;
		if(cnt!=0){
			printf("\n");
		}
		for(i=a;i<=b;i++){
			if(i%4==0){
				if(i%100!=0){
					printf("%d\n",i);
					flg=1;
				}
			}
			else if(i%400==0){
				printf("%d\n",i);
				flg=1;
			}
			cnt++;
		}
		if(flg==0){
			printf("NA\n");
		}
		scanf("%d %d",&a,&b);
	}
	return 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);
        printf("\n");
        scanf("%d %d", &a, &b);
    }
    printf("\n");
    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>
using namespace std;
void uruu(int, bool&);

int main() {
	int a, b;

	while (true) {
		cin >> a >> b;
		if (a == 0 && b == 0) break;
		bool flag = true;

		for (int i = a;i <= b;i++) {
			uruu(i, flag);
		}
		if (flag)cout << "NA" << endl;
	}

	return 0;
}

void uruu(int year, bool& flag) {
	if (year % 400 == 0) {
		cout << year << endl;
		flag = false;
		return;
	}
	else if (year % 100 == 0) {
		return;
	}
	else if (year % 4 == 0) {
		cout << year << endl;
		flag = false;
		return;
	}
	else {
		return;
	}
}

C++:  #include<iostream>
 #include<stdio.h>
 #include<cstdlib>
 #include<cstdio>
 #include<string>
 #include<math.h>
 #include<iomanip>
 #include<algorithm>
 #include<string.h>
 #include<cctype>
 #include<map>
 #include<set>
 #include<vector>
 #include<sstream>
 #include<stack>
 #include<queue>
 #include<deque>
 #include<functional>
 #include<utility>
 #include<list>
 
 using namespace std;
 
 bool isLeap(int year)
 {
   if(year%4!=0) return false;
   else
   {
     if(year%100==0)
     {
       if(year%400==0) return true;
       else return false;               
     }
     else return true;    
   }     
 }
 
 int main()
 {
   int start,end;
   bool flag=false;
   while(cin>>start>>end&&(start||end))
   {
     if(flag) cout<<endl;
     int count=0;
     for(int i=start;i<=end;i++)
     {
       if(isLeap(i))
       {
         cout<<i<<endl; 
         count++;
       }        
     }                       
     if(!count) cout<<"NA"<<endl;
     //cout<<endl; 
     flag=true;            
   }
   //while(1);
   return 0;
 }