Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)
const INF = 0x7FFFFFFF

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		chairs := make([]string, n)
		for i := range chairs {
			chairs[i] = "#"
		}
		sit := func(who string) {
			if who == "A" {
				chairs[getStringIndex(chairs, "#")] = "A" // A国の人は左から見て行って空いている席を見つけ次第座る
				// log.Println(chairs)
			} else if who == "B" {
				f := true
				for i := n-1; i > -1; i-- {
					// B国の人はA国人の隣以外で、右端から空いている椅子に座る
					if chairs[i] == "#" && (i == 0 || chairs[i-1] != "A") && (i == n-1 || chairs[i+1] != "A") {
								chairs[i] = "B"
								f = false
								break
					}
				}
				// A国人の隣しか空いていない場合、我慢して左端から空いている椅子に座る
				if f {
					chairs[getStringIndex(chairs, "#")] = "B"
				}
				// log.Println(chairs)
			} else if who == "C" { // C国人は人の隣に座りたい
				for i := 0; i < n; i++ {
					if chairs[i] != "#" {
						if i + 1 <= n-1 && chairs[i+1] == "#" {
							chairs[i+1] = "C"
							break
						} else if i - 1 >= 0 && chairs[i-1] == "#" {
							chairs[i-1] = "C"
							break
						}
					}
				}
				// log.Println(chairs)
			} else { // who == "D"
				// D国の人は人から離れて座りたい
				// どうしても誰かの隣に座らなければならない場合、その中で一番左側にある椅子に座る
				scores := make([]int, n)
				for i := range scores {
					scores[i] = INF
				}
				for i, v := range chairs {
					if v == "#" {
						scores[i]++
					}
				}
				for i := n-1; i > -1; i-- {
					tmp := 0
					if chairs[i] == "#" {
						tmp++
					} else {
						tmp = 0
					}
					scores[i] = min(scores[i], tmp)
				}
				chairs[getIntIndex(scores, getMax(scores))] = "D"
				// log.Println(chairs)
			}
		}
		scanner.Scan()
		if first := scanner.Text(); first == "A" || first == "D" {
			chairs[0] = first
		} else if first == "B" {
			chairs[len(chairs)-1] = "B"
		} else {
			chairs[n/2] = "C"
		}
		// log.Println(chairs)
		for i := 0; i < m-1; i++ {
			scanner.Scan()
			sit(scanner.Text())
		}
		fmt.Println(strings.Join(chairs, ""))
	}
}

func getStringIndex(chairs []string, who string) int {
	for i, v := range chairs {
		if v == who {
			return i
		}
	}
	return -1
}

func getIntIndex(scores []int, target int) int {
	for i, v := range scores {
		if v == target {
			return i
		}
	}
	return -1
}

func min(a, b int) int {
	if a > b {
		return b
	}
	return a
}

func getMax(scores []int) int {
	tmp := -1
	for _, v := range scores {
		if tmp < v {
			tmp = v
		}
	}
	return tmp
}

C++: #include<stdio.h>   //????§£?±?
#include<string.h>
#include<math.h>
int main(void)
{
	int a,s,d[100],f,g,h,i,j,k,c,x[3],o;
	char z[2];
	while(1){
		scanf("%d %d",&a,&s);
		if(a==0&&s==0) break;
		f=a;
		for(i=0;i<a;i++) d[i]=0;
		for(i=0;i<s;i++){
			scanf("%s",z);
			if(z[0]=='A'){
				for(j=0;j<a;j++){
					if(d[j]==0){
						d[j]=1;
						f--;
						break;
					}
				}
			}
			else if(z[0]=='B'){
				g=0;
				for(j=a-1;j>=0;j--){
					if(d[j]==0&&d[j+1]!=1&&d[j-1]!=1){
						d[j]=2;
						f--;
						break;
					}
					if(d[j]==0) g++;
					if(f==g){
						d[j]=2;
						f--;
						break;
					}
				}
			}
			else if(z[0]=='C'){
				if(a==f){
					if(a%2==1){
						d[((a+1)/2-1)]=3;
						f--;
					}
					else if(a%2==0){
						d[a/2]=3;
						f--;
					}
				}
				else if(a>f){
					for(j=0;j<a;j++){
						if(d[j]>0){
							if(d[j-1]==0&&j-1>=0){
								d[j-1]=3;
								f--;
								break;
							}
							else if(d[j+1]==0&&j+1<a){
								d[j+1]=3;
								f--;
								break;
							}

						}
					}
				}
			}
			else if(z[0]=='D'){
				h=-1;
				c=-1;
				int v=0;
				x[0]=0;
				x[1]=0;
				for(j=a-1;j>=0;j--){
					if(d[j]>0&&v==0){
						h=j;
						if(d[0]==0){
							x[0]=h-1;
							x[1]=0;
						}
						v=1;
					}
					else if(d[j]>0&&v==1){
						c=j;
					}
					if(c>-1&&h>-1){
						if((h-c)%2==1){
							if(x[0]<=((h-c)/2-1)){
								x[0]=(h-c)/2-1;
								x[1]=h-(h-c)/2-1;
							}
						}
						else if((h-c)%2==0){
							if(x[0]<=(h-c)/2){
								x[0]=(h-c)/2;
								x[1]=h-(h-c)/2;
							}
						}
					}
					if(c>-1) h=c;
				}
				if(d[a-1]==0){
					if(x[0]<(a-1)-c){
						x[0]=(a-1)-c;
						x[1]=a-1;
					}
				}
				if(h==-1) x[1]=0;
				else if(c==-1){
					x[0]=(a-1)-h;
					x[1]=a-1;
					if(x[0]<h) x[1]=0;
				}
				d[x[1]]=4;
				f--;
			}
		}
		for(i=0;i<a;i++){
			if(d[i]==0) printf("#");
			else if(d[i]==1) printf("A");
			else if(d[i]==2) printf("B");
			else if(d[i]==3) printf("C");
			else if(d[i]==4) printf("D");
		}
		printf("\n");
	}
	return 0;
}

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

char chair[128];
int n, m;
const int M = 2;

void A() {
	for(int i = 0; i < n; i++) {
		if(chair[i+M] == 'N') {
			chair[i+M] = 'A';
			break;
		}
	}
}

void B() {
	for(int i = n-1; i >= 0; i--) {
		if(chair[i+M] == 'N' && chair[i+1+M] != 'A' && chair[i-1+M] != 'A') {
			chair[i+M] = 'B';
			return;
		}
	}
	for(int i = 0; i < n; i++) {
		if(chair[i+M] == 'N') {
			chair[i+M] = 'B';
			return;
		}
	}
}

void C() {
	for(int i = 0; i < n; i++) {
		if(chair[i+M] == 'N' && (chair[i-1+M] != 'N' || chair[i+1+M] != 'N')) {
			chair[i+M] = 'C';
			return;
		}
	}
	chair[(n+1)/2+M] = 'C';
}

void D() {
	int mx = 0;
	int indx = 0;
	for(int i = 0; i < n; i++) {
		if(chair[i+M] == 'N') {
			int mn = 1000;
			for(int j = 0; j < n; j++) {
				if(chair[j+M] != 'N') {
					if(mn > abs(j - i))
						mn = abs(j - i);
				}
			}
			if(mn > mx) {
				mx = mn;
				indx = i;
			}
		}
	}
	chair[indx+M] = 'D';
}

int main() {
	while(cin >> n >> m, n || m) {
		for(int i = 0; i < 128; i++)
			chair[i] = 'N';
		for(int i = 0; i < m; i++) {
			string s;
			cin >> s;
			if(s[0] == 'A')
				A();
			else if(s[0] == 'B')
				B();
			else if(s[0] == 'C')
				C();
			else
				D();
		}
		for(int i = 0; i < n; i++) {
			cout << (chair[i+M] == 'N' ? '#' : chair[i+M]);
		}
		cout << endl;
	}
}

C++: #include<iostream>

char *chr, *peo;
int n,m;

void sitA(int i){
	for(int k=0; k<n; k++){
		if(chr[k] == '#'){
			chr[k] = 'A';
				break;
		}
	}
	return;
}

void sitB(int i){
	if(chr[n-1]=='#' && chr[n-2] != 'A'){
		chr[n-1] = 'B';
		return;
	}
	for(int k=n-2; k>0; k--){
		if(chr[k] == '#' && chr[k-1] != 'A' && chr[k+1] != 'A'){
			chr[k] = 'B';
			return;
		}
	}
	if(chr[0]=='#' && chr[1] != 'A'){
		chr[0] = 'B';
		return;
	}	
	for(int k=0; k<n; k++){
		if(chr[k] == '#'){
			chr[k] = 'B';
			return;
		}
	}
}

void sitC(int i){
	if(i==0){
		if(n%2 == 0)
			chr[(n/2)+1] = 'C';
		else
			chr[(n+1)/2] = 'C';
		return;
	}
	for(int k=0; k<n; k++){
		if(chr[k] == '#')
			continue;
		if(k>0){
			if(chr[k-1] == '#'){
				chr[k-1] = 'C';
				return;
			}
		}
		if(k<n-1){
			if(chr[k+1] == '#'){
				chr[k+1] = 'C';
				return;
			}
		}
	}
}

void sitD(int i){
	if(i==0){
		chr[0] = 'D';
		return;
	}
	int ans,tmp=0,tmp1,tmp2;
	for(int k=0; k<n; k++){
		if(chr[k] == '#'){
			ans = k;
			break;
		}
	}
	for(int k=ans; k<n; k++){
		if(chr[k] != '#')
			continue;
		tmp1=0;
		tmp2=0;
		if(k<n-1){
			for(int t=k+1; t<n; t++){
				if(chr[t] != '#')
					break;
				tmp1++;
			}
		}
		if(k>0){
			for(int t=k-1; t>=0; t--){
				if(chr[t] != '#')
					break;
				tmp2++;
			}
		}
		if(tmp1 > tmp2)
			tmp1 = tmp2;
		if(tmp1 > tmp){
			tmp = tmp1;
			ans = k;
		}
	}
	chr[ans] = 'D';
}

void solve(){
	char tmp;
	for(int i=0; i<m; i++){
		tmp = peo[i];
		switch(tmp){
		case 'a':
		case 'A':
			sitA(i);
			break;
		case 'b':
		case 'B':
			sitB(i);
			break;
		case 'c':
		case 'C':
			sitC(i);
			break;
		case 'd':
		case 'D':
			sitD(i);
			break;
		}
	}
	std::cout << chr << std::endl;
}

int main(){
	while(true){
		std::cin >> n >> m;
		if(!n && !m)
			return 0;
		chr = new char[n];
		peo = new char[m];
		for(int i=0; i<n; i++){
			chr[i] = '#';
			if(i>=m)
				chr[i] = '#';
			else
				std::cin >> peo[i];
		}
		solve();
		delete[] chr;
		delete[] peo;
	}
}