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 <cstdio>
#include <vector>
#define _USE_MATH_DEFINES
#include <math.h>
#include <cstring>
#include <numeric>
#include <algorithm>
#include <stdlib.h>
#include <functional>
#include <string>

#include <fstream>
#include <iomanip>
#include <array>
#include <map>
#include <queue>
#include <limits.h>
#include <set>
#include <stack>
#include <random>
#include <complex>
#include <unordered_map>
#include <nmmintrin.h>
#include <chrono>
#define rep(i,s,n) for(int i = (s); (n) > i; i++)
#define REP(i,n) rep(i,0,n)
#define RANGE(x,a,b) ((a) <= (x) && (x) <= (b))
#define DUPLE(a,b,c,d) (RANGE(a,c,d) || RANGE(b,c,d) || RANGE(c,a,b) || RANGE(d,a,b))
#define INCLU(a,b,c,d) (RANGE(a,c,d) && (b,c,d))
#define PW(x) ((x)*(x))
#define ALL(x) (x).begin(), (x).end()
#define MODU 1000000007
#define bitcheck(a,b)   ((a >> b) & 1)
#define bitset(a,b)      ( a |= (1 << b))
#define bitunset(a,b)    (a &= ~(1 << b))
#define MP(a,b) make_pair((a),(b))
#define Manh(a,b) (abs((a).first-(b).first) + abs((a).second - ((b).second))
#define pritnf printf
#define scnaf scanf
#define itn int
#ifdef _MSC_VER
#define __builtin_popcount _mm_popcnt_u32
#define __builtin_popcountll _mm_popcnt_u64
#endif
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
ll gcd(ll a, ll b) {
	if (b == 0) return a;
	return gcd(b, a%b);
}
template<typename A, size_t N, typename T>
void Fill(A(&array)[N], const T &val) {
	std::fill((T*)array, (T*)(array + N), val);
}

struct Edge {
	int from, to, weight;

	bool operator < (const Edge& obj) const {
		return weight < obj.weight;
	}
	bool operator > (const Edge& obj) const {
		return weight > obj.weight;
	}
};

struct UnionFind {
	vector<int> data;
	UnionFind(int size) : data(size, -1) { }
	bool unionSet(int x, int y) { //????????\??£??????????????¨ y?????\??£?????????????????????
		x = root(x); y = root(y);
		if (x != y) {
			if (data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) { //x??¨y????????????????????\??£??????????????????????????????
		return root(x) == root(y);
	}
	int root(int x) {
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	bool isroot(int x) {
		return data[x] < 0;
	}
	int size(int x) {
		return -data[root(x)];
	}
};

int arr[100001];
void Eratosthenes(int N) {//N?????§????´???°??¨
	for (int i = 0; i < N; i++) {
		arr[i] = 1;
	}
	for (int i = 2; i < sqrt(N); i++) {
		if (arr[i]) {
			for (int j = i * 2; j <= N; j += i) {
				arr[j] = 0;
			}
		}
	}
}

int main()
{
	while (1) {

	int a, b;
	cin >> a >> b;

	if (a == 0 && b == 0) break;

	int cou = 0;
	rep(i, a, b + 1) {
		if ((i % 4) == 0 && i % 100) cou++;
		else if ((i % 400) == 0) cou++;
	}

	}
	return 0;
}

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

int uru(int y);

int main(void){
	bool f;
	int a,b;	
		f=true;
		for(int i=a;i<=b;i++){
			if(uru(i)){
				f=false;
				cout<<i<<endl;
			}
		}
		if(f)cout<<"NA"<<endl;
	while(cin>>a>>b,a!=0||b!=0){
		cout<<endl;
		f=true;
		for(int i=a;i<=b;i++){
			if(uru(i)){
				f=false;
				cout<<i<<endl;
			}
		}
		if(f)cout<<"NA"<<endl;
	}

}


int uru(int y){
	if(y%4==0){
		if(y%100==0){
			if(y%400==0)return 1;
			return 0;
		}
		return 1;
	}
	return 0;
}

C++: #include <iostream>

bool judge_uruyear(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 print_uruyear(int year_begin, int year_end)
{

    int count_year = 0;

    for(int i = year_begin; i < year_end; i++) {
        if (judge_uruyear(i)) {
            count_year += 1;
            std::cout << i << std::endl;
        }    
    }

    if(count_year == 0) {
        std::cout << "NA" << std::endl;
    }

    std::endl(std::cout);

}

int main()
{

    int year_begin, year_end;

    while(true) {
        
        std::cin >> year_begin >> year_end;
        
        if(year_begin == 0 && year_end ==0) {
            break;
        }
        
        print_uruyear(year_begin, year_end);

    }
    
    return 0;
}

C++: #include<stdio.h>

void leap_year(int start_year, int end_year);

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

void leap_year(int start_year, int end_year)
{
 int n = 0;
 int year = start_year;
   while (year <= end_year){
     if (year % 400 == 0 || (year % 100 != 0 && year % 4 == 0)){
     printf("%d\n", year);
     n++;
   }
     year++;
 }
 if (n == 0){
   printf("NA\n");
  }
}

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;
    }
    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<iostream>
using namespace std;

bool is_reap(int i){
	if(!(i%100) && (i%400)) return false;
	if(!(i%4)) return true;
	return false;
}

int main()
{
	int a, b;
	bool flag = false;
	while(cin >> a >> b){
		if(!a && !b) break;
		if(flag)cout << endl;
		flag = true;
		bool flag = false;
		for(int i=a; i<=b; i++){
			if(is_reap(i)){ cout << i << endl; flag = true;}
		}
		if(!flag) cout << "NA" << endl;

	}
	return 0;
}