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
		}
		chair := make([]string, n+1)
		for i := range chair {
			chair[i] = "#"
		}
		chair[n] = "Sentinel"
		for i := 0; i < m; i++ {
			scanner.Scan()
			switch who := scanner.Text(); who {
			case "A": // 左から眺めて行って空いている席があったら即座に座る
				for j := 0; j < n; j++ {
					if chair[j] == "#" {
						chair[j] = "A"
						break
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "B":
				flag := true
				// 右端からAの隣でない席を探していく
				for j := n-1; j > -1; j-- {
					if chair[j] == "#" && (j == 0 || chair[j-1] != "A") && chair[j+1] != "A" {
						flag = false
						chair[j] = "B"
						break
					}
				}
				// Aの隣しか空いていないので一番左端の空いている席に座る
				if flag {
					for j := 0; j < n; j++ {
						if chair[j] == "#" {
							chair[j] = "B"
							break
						}
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "C":
				if i == 0 {
					chair[n/2] = "C" // 先客が誰もいないときは真ん中の椅子に座る
				} else {
					for j := 0; j < n; j++ { // 左から舐めて
						if chair[j] != "#" { // その席が空いていなくて
							if chair[j+1] == "#" { // 右隣が空いているなら座る
								chair[j+1] = "C"
								break
							} else if j != 0 && chair[j-1] == "#" { // 右隣が空いていないので左隣に座る
								chair[j-1] = "C"
								break
							}
						}
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "D":
				distanceTable := make([]int ,n)
				for j := range distanceTable {
					distanceTable[j] = INF
				}
				for j:= 0; j < n; j++ {
					if chair[j] != "#" {
						for k := 0; k < n; k++ {
							distanceTable[k] = min(distanceTable[k], abs(j-k))
						}
					}
				}
				// log.Println("distanceTAble:", distanceTable)
				at := 0
				distance := 0
				for j := 0; j < n; j++ {
					if distance < distanceTable[j] {
						at = j
						distance = distanceTable[j]
					}
				}
				chair[at] = "D"
				// log.Println(chair)
				break // 次の人を読み込む
			}
		}
		fmt.Println(strings.Join(chair, ""))
	}
}

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

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

C++: #include<iostream>
#include<algorithm>

using namespace std;
#define INF (1 << 29)
int main(){
  char chair[105];
  int n, m;
  char c;
  while(cin >> n >> m, n){
    fill(chair, chair + n, '#');
    chair[n] = 0;
    for(int i = 0;i < m;i++){
      cin >> c;
      switch(c){
      case 'A':
      left :
	for(int j = 0;j < n;j++){
	  if(chair[j] == '#'){
	    chair[j] = c;
	    break;
	  }
	}
	break;
      case 'B':
	for(int j = n - 1;j >= 0;j++){
	  if((j == 0 || chair[j - 1] != 'A') && chair[j] == '#' && chair[j + 1] != 'A'){
	    chair[j] = c;
	    break;
	  }
	  if(j == 0)goto left;
	}
	break;
      case 'C':
	for(int j = 0;j < n;j++){
	  if(j != '#'){
	    if(chair[j + 1] == '#'){
	      chair[j + 1] = c;
	      break;
	    }
	    if(j != 0 && chair[j - 1] == '#'){
	      chair[j - 1] = c;
	      break;
	    }
	  }
	  if(j == n - 1){
	    chair[n / 2] = c;
	  }
	}
	break;
      case 'D':
	int p = 0, s = -1;
	for(int j = 0;j < n;j++){
	  if(chair[j] != '#')continue;
	  int t = INF;
	  for(int k = j;k < n;k++){
	    if(chair[k] != '#'){
	      t = k - j;
	    }
	  }
	  for(int k = j;k >= 0;k--){
	    if(chair[k] != '#'){
	      t = min(t, j - k);
	    }
	  }
	  if(t > s){
	    p = j;
	    s = t;
	  }
	}
	if(p == INF){
	  chair[n - 1] = c;
	}
	else{
	  chair[p] = c;
	}
	break;
      }
    }
    printf("%s\n", chair);
  }
  return 0;
}

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<a){
								d[j+1]=3;
								f--;
								break;
							}
							else if(d[j-1]==0&&j-1>=0){
								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>

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;
		}
	}
	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] = 'C';
		else
			chr[(n-1)/2] = 'C';
		return;
	}
	for(int k=0; k<n; k++){
		if(chr[k] == '#')
			continue;
		if(k<n-1){
			if(chr[k+1] == '#'){
				chr[k+1] = 'C';
				return;
			}
		}
		if(k>0){
			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(t == n-1)
					tmp1 = n+1;
			}
		}
		else
			tmp1 = n+1;
		if(k>0){
			for(int t=k-1; t>=0; t--){
				if(chr[t] != '#')
					break;
				tmp2++;
				if(t == 0)
					tmp2 = n+1;
			}
		}
		else
			tmp2 = n+1;
		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)
				std::cin >> peo[i];
		}
		solve();
		delete[] chr;
		delete[] peo;
	}
}