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>
using namespace std;

int judge(int n){
  int flg = 0;
  if(n%4 == 0){
    if(n%400 == 0) return 1;
    else if(n%100 == 0) return 0;
    return 1;  
   }
  return 0;
}

int main(){
  int f,e;

  while(1){
    int cnt = 0;
    cin >> f >> e;
    if(f == 0 && e == 0) break;

    for(int i = f ; i <= e ; i++){
      if(judge(i)){
        cout << i << endl;
        cnt++;
      }
    }
    if(cnt == 0) cout << "NA" << endl;
    cout << endl;
  }

  return 0;
}

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

bool judge(int year);

int main() 
{
	int start, end;
	
	while (true) {
		int check = 0;
		std::cin >> start >> end;
		
		if (start == 0 && end == 0) {
			break;
		}
		
		for (int i = start; i <= end; i++) {
			if (judge(i)) {
				std::cout << i << std::endl;
				check = 1;
			}
		}
		
		if (check == 0) {
			std::cout << "NA" << std::endl;
		}
		
		std::cout << std::endl;
	}
	return 0;
}


bool judge(int year){
	if ((year % 4 == 0 && !(year % 100 == 0)) || year % 400 == 0) {
		return true;
	} else {
		return false;
	}
}

C++: #include<iostream>

bool isuru( int y )
{
 	return ( y % 4 == 0 && y % 100 != 0 ) || y % 400 == 0;
}

int main()
{
	int a, b;
	bool init = true;
	
	while( 1 ){
		std::cin >> a >> b;
		
		if( !a && !b )break;
		
		if( !init ) std::cout << std::endl;
		
		init = false;
		
		bool f = false;
		
		for( int i = a; i <= b; i++ ){
			if( isuru( i ) ){
				std::cout << i << std::endl;
				f = true;
			}
		}
		
		if( !f ){
		 	std::cout << "NA" << std::endl;
		}
	}

 	return 0;
}

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()
{
	int fas = true;
	while (1) {
	int a, b;
	cin >> a >> b;
		if (!fas) cout << endl;

	if (a == 0 && b == 0) break;
	bool f = false;
	rep(i, a, b + 1) {
		if ((i % 4) == 0 && i % 100) f = 1, cout << i << endl;
		else if ((i % 400) == 0) f = 1, cout << i << endl;
	}
	if(!f)cout << "NA" << endl;
	fas = false;
	}
	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<bits/stdc++.h>
#define REP(i,n) for(int i=0;i<n;i++)
#define LOOP(i,x,n) for(int i=x;i<n;i++)
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define MP make_pair
#define FR first
#define SC second
#define int long long
using namespace std;
const int MOD=1000000007;
const int INF=9000000009;


signed main(){
  int a,b;
  int f=0;
  while(cin>>a>>b,a){
    if(f)cout<<endl;
    f=1;
    vector<int> y;
    for(int i=a;i<=b;i++){
      if(i%4==0){
        if(i%100!=0){
          y.PB(i);
          continue;
        }
        if(i%400==0)y.PB(i);
      }
    }
    if(y.size()==0){
      cout<<"NA"<<endl;
    }else{
      for(auto x:y)cout<<x<<endl;
    }
  }
  return 0;
}