Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	for n := getNextInt(scanner); n > 0; n = getNextInt(scanner) {
		tt := make([]team, n)
		for i := 0; i < n; i++ {
			tt[i].id = getNextInt(scanner)
			tt[i].uni = getNextInt(scanner)
			tt[i].ac = getNextInt(scanner)
			tt[i].pn = getNextInt(scanner)
		}
		sort.SliceStable(tt, func(i, j int) bool {
			if tt[i].ac == tt[j].ac {
				if tt[i].pn == tt[j].pn {
					return tt[i].id < tt[j].id
				}
				return tt[i].pn < tt[j].pn
			}
			return tt[i].ac > tt[j].ac
		})
		cc := make([]int, 100005)
		ans := make([]int, 0)
		for i := 0; i < n; i++ {
			if cc[0] < 10 && cc[tt[i].uni] < 3 {
				cc[0]++
				cc[tt[i].uni]++
				ans = append(ans, tt[i].id)
				continue
			}
			if cc[0] < 20 && cc[tt[i].uni] < 2 {
				cc[0]++
				cc[tt[i].uni]++
				ans = append(ans, tt[i].id)
				continue
			}
			if cc[0] < 26 && cc[tt[i].uni] < 1 {
				cc[0]++
				cc[tt[i].uni]++
				ans = append(ans, tt[i].id)
				continue
			}
		}
		for i := 0; i < len(ans); i++ {
			fmt.Fprintln(writer, ans[i])
		}
	}
}

type team struct {
	id, uni, ac, pn int
}

C++: #include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define RFOR(i,a,b) for(int i=(b) - 1;i>=(a);i--)
#define REP(i,n) for(int i=0;i<(n);i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)

#define PB push_back
#define MP make_pair
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define CLR(a) memset(a,0,sizeof(a))
#define SET(a,c) memset(a,c,sizeof(a))

#define DEBUG(x) cout<<"#x"<<": "<<x<<endl

using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<ll> vl;

const ll INF = INT_MAX/3;
const ll MOD = 1000000007;
const double EPS = 1e-14;
const int dx[] = {1,0,-1,0} , dy[] = {0,1,0,-1};

vector<bool> used;
vector<int> count_t;
vector<bool> isDecided;
vector<bool> ans;

int main(){
    while(true){
	int n;
	vector< pair< pair<int,int> , pair<int,int> > > t;
	cin >> n;
	if(n==0) break;
	REP(i,n){
	    int I,A,U,P;
	    cin >> I >> U >> A >> P;
	    t.PB( MP( MP(-A,P) , MP(I,U) ) );
	    sort(ALL(t));
	}
	used = vector<bool>(2000,false);
	count_t = vector<int>(2000,0);
	isDecided = vector<bool>(2000,false);
	int temp = 0;

	REP(i,n){
	    if(!used[t[i].second.second-1]){
		used[t[i].second.second-1] = true;
		count_t[t[i].second.second-1]++;
		isDecided[t[i].second.first-1] = true;
		temp++;
	    }
	}

	if(temp < 10){
	    REP(i,n){
		if(!isDecided[t[i].second.first-1] && count_t[t[i].second.second-1] < 3){
		    count_t[t[i].second.second-1]++;
		    isDecided[t[i].second.first-1] = true;
		    temp++;
		}
	    }
	}


	if(temp < 20){
	    REP(i,n){
		if(!isDecided[t[i].second.first-1] && count_t[t[i].second.second-1] < 2){
		    count_t[t[i].second.second-1]++;
		    isDecided[t[i].second.first-1] = true;
			temp++;
		}
	    }
	}

	if(temp < 26){
	    REP(i,n){
		if(!isDecided[t[i].second.second-1] && count_t[t[i].second.second-1] < 1){
		    count_t[t[i].second.second-1]++;
		    isDecided[t[i].second.first-1] = true;
		    temp++;
		}
	    }
	}

	REP(i,n){
	    if(isDecided[t[i].second.first-1]) cout << t[i].second.first << endl;
	}
    }

    return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<map>

using namespace std;

class team {
public:
	int kasu[4];
	team(int a, int b, int c, int d){
		
		kasu[0] = a;//id
		kasu[1] = b;//????±?
		kasu[2] = c;//??£?§£
		kasu[3] = d;//??????
	}
	int back(int a) {
		return kasu[a];
	}
};

vector<team> t;
map<int, int> mp;
vector<int> res;
vector<vector<int>> l (10, vector<int>(0));
int n;

int val(int x, int y) {
	for (int i = 0; i < y; i++) {
		x /= 10;
	}
	return x % 10;
}

void kitei(int x, int y) {//???????????????????????°, ???
	for (int i = 0; i < 10; i++) {
		l[i].push_back(-1);
	}
	for (int i = 0; i < 10; i++) {
		while (l[i][0] != -1) {
			l[val(t[l[i][0]].kasu[x], y)].push_back(l[i][0]);//?????°??????????????????????????£??????
			l[i].erase(l[i].begin());//?¶????
		}
		l[i].erase(l[i].begin());
	}
	return;
}

int main() {
	while (1) {
		cin >> n;
		if (n == 0)
			break;
		for (int i = 0; i < n; i++) {
			int a, b, c, d;
			cin >> a >> b >> c >> d;
			t.emplace_back(a, b, c, d);
			l[0].push_back(i);
		}
		for (int i = 0; i < 6; i++) {//??????????????£????????????
			kitei(3, i);
		}
		kitei(2, 0);
		int num = 0;
		for (int i = 9; i >= 0; i--) {
			for (int j = 0; j < l[i].size(); j++) {
				if (num < 10) {
					if (mp[t[l[i][j]].kasu[1]] < 3) {
						res.push_back(t[l[i][j]].kasu[0]);
						num++;
						mp[t[l[i][j]].kasu[1]]++;
					}
				}
				else if (num < 20) {
					if (mp[t[l[i][j]].kasu[1]] < 2) {
						res.push_back(t[l[i][j]].kasu[0]);
						num++;
						mp[t[l[i][j]].kasu[1]]++;
					}
				}
				else if (num < 26) {
					if (mp[t[l[i][j]].kasu[1]] < 1) {
						res.push_back(t[l[i][j]].kasu[0]);
						num++;
						mp[t[l[i][j]].kasu[1]]++;
					}
				}
			}
		}
		for (auto q : res) {
			cout << q << endl;
		}
	}

	return 0;
}