Go: package main

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

var scanner = bufio.NewScanner(os.Stdin)

type Point struct {
	x, y int
}

func main() {
	dx := []int{1, 0, -1, 0}
	dy := []int{0, -1, 0, 1}
	maze := make([][]rune, 30)
	for i := range maze {
		maze[i] = make([]rune, 30)
	}
	next := make([][]rune, 30)
	for i := range next {
		next[i] = make([]rune, 30)
	}
	check := make([][]int, 30)
	for i := range check {
		check[i] = make([]int, 30)
	}
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		W, _ := strconv.Atoi(buf[0])
		H, _ := strconv.Atoi(buf[1])
		if W == 0 && H == 0 {
			break
		}
		for i := 0; i < H; i++ {
			scanner.Scan()
			buf_ := scanner.Text()
			for j, v := range buf_ {
				maze[i][j] = v
			}
		}
		man := 0
		for i := 0; i < H; i++ {
			for j := 0; j < H; j++ {
				if maze[i][j] != '.' && maze[i][j] != 'X' && maze[i][j] != '#' {
					switch maze[i][j] {
					case 'E':
						maze[i][j] = 0
						man++
					case 'N':
						maze[i][j] = 1
						man++
					case 'W':
						maze[i][j] = 2
						man++
					case 'S':
						maze[i][j] = 3
						man++
					}
				}
			}
		}
		ans := -1
		for t := 0; t <= 180; t++ {
			if man == 0 {
				ans = t
				break
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					check[i][j] = 0x7FFFFFFF
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					if maze[i][j] > 3 {
						continue
					}
					l := (maze[i][j] + 3) % 4
					for k := 0; k < 4; k++ {
						y := i + dy[l]
						x := j + dx[l]
						if 0 <= y && y < H && 0 <= x && x < W && (maze[y][x] == '.' || maze[y][x] == 'X') {
							maze[i][j] = l
							check[y][x] = min(check[y][x], int((l+2)%4))
							break
						}
						l = (l + 1) % 4
					}
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					next[i][j] = maze[i][j]
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					if maze[i][j] > 3 {
						continue
					}
					y := i + dy[maze[i][j]]
					x := j + dx[maze[i][j]]
					if 0 <= y && y < H && 0 <= x && x < W && check[y][x] == int((maze[i][j]+2)%4) {
						if maze[y][x] == '.' {
							next[y][x] = maze[i][j]
						} else if maze[y][x] == 'X' {
							man--
						}
						next[i][j] = '.'
					}
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					maze[i][j]=next[i][j]
				}
			}
		}
		if ^ans != 0 {
			fmt.Println(ans)
		} else {
			fmt.Println("NA")
		}
	}
}

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

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

using namespace std;

const int N = 30;

int h, w, p;
char mapData[N][N];
bool used[N][N];
int dy[] = {0, -1, 0, 1};
int dx[] = {1, 0, -1, 0};

int convertDirection(char c){
   if(c == 'E') return 0;
   if(c == 'N') return 1;
   if(c == 'W') return 2;
   if(c == 'S') return 3;
}

char convertInteger(int d){
   if(d == 0) return 'E';
   if(d == 1) return 'N';
   if(d == 2) return 'W';
   if(d == 3) return 'S';
}

void changeDirection(int y, int x, char c){
   int td = (convertDirection(c)+3)%4;
   for(int i=0;i<4;++i){
      int d = (td+i)%4;
      int ty = y + dy[d];
      int tx = x + dx[d];
      if(ty<0 || ty>=h) continue;
      if(tx<0 || tx>=w) continue;
      if(!(mapData[ty][tx] == '.' || mapData[ty][tx] == 'X')) continue;
      mapData[y][x] = convertInteger(d);
      return;
   }
}

void searchPerson(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         if(mapData[i][j] == 'E' || 
            mapData[i][j] == 'N' || 
            mapData[i][j] == 'W' ||
            mapData[i][j] == 'S')
            changeDirection(i, j, mapData[i][j]);
      }
   }
}

void movePerson(int y, int x){
   int d = convertDirection(mapData[y][x]);
   int ty = y + dy[d];
   int tx = x + dx[d];
   if(mapData[ty][tx] == 'X'){
      --p;
   }else{
      mapData[ty][tx] = mapData[y][x];
   }
   mapData[y][x] = '.';
}

void selectPerson(int y, int x){
   for(int i=0;i<4;++i){
      int ty = y + dy[i];
      int tx = x + dx[i];
      if(ty<0 || ty>=h) continue;
      if(tx<0 || tx>=w) continue;
      if(mapData[ty][tx] == '#' || mapData[ty][tx] == '.' || mapData[ty][tx] == 'X') continue;
      if(used[ty][tx]) continue;
      if(abs(i-convertDirection(mapData[ty][tx])) == 2){
         movePerson(ty, tx);
         used[y][x] = used[ty][tx] = true;
         break;
      }
   }
}

void searchPoint(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         if(!(mapData[i][j] == '.' || mapData[i][j] == 'X')) continue;
         selectPerson(i, j);
      }
   }
}

main(){
   while(cin >> w >> h && (h || w)){
      p = 0;
      for(int i=0;i<h;++i){
         for(int j=0;j<w;++j){
            cin >> mapData[i][j];
            if(mapData[i][j] == 'E' || 
               mapData[i][j] == 'N' || 
               mapData[i][j] == 'W' ||
               mapData[i][j] == 'S')
               ++p;
         }
      }
      if(p == 0){
         cout << 0 << endl;
         continue;
      }
      for(int t=1;;++t){
         if(t > 180){
            cout << "NA" << endl;
            break;
         }
         fill(used[0], used[N], false);
         searchPerson();
         searchPoint();
         if(p == 0){
            cout << t << endl;
            break;
         }
      }
   }
   return 0;
}

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

typedef pair<int,int> P;

int dir(char a){
  if(a=='E')return 0;
  if(a=='N')return 1;
  if(a=='W')return 2;
  if(a=='S')return 3;
  return -1;
}

char inv_dir(int a){
  if(a==0)return 'E';
  if(a==1)return 'N';
  if(a==2)return 'W';
  return 'S';
}

int main(){
  int h,w;
  string grid[100];
  int dx[] = {1,0,-1,0},dy[] = {0,-1,0,1};

  while(cin >> w >> h && (w||h)){
    for(int i=0;i<h;i++)cin >> grid[i];

    int ans = 0;
    while(ans<=180){
      set<P> s;
      int num = 0;
      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++){
	  int d = dir(grid[i][j]);
	  if(0<=d){
	    num++;
	    for(int k=-1;k<3;k++){
	      int dd = (d+k+4)%4;
	      int sy = i+dy[dd], sx = j+dx[dd];
	      //if(sy<0 || sx<0 || h<=sy || w<=sx)continue;
	      if(grid[sy][sx] == '.' || grid[sy][sx] == 'X'){
		grid[i][j] = inv_dir(dd);
		s.insert(P(sy,sx));
		break;
	      }
	    }
	  }
	}
      }
      if(!num)break;
      set<P>::iterator ite;
      for(ite=s.begin();ite!=s.end();ite++){
	P p = *ite;
	for(int i=0;i<4;i++){
	  int sy = p.first+dy[i], sx = p.second+dx[i];
	  //if(sy<0 || sx<0 || h<=sy || w<=sx)continue;
	  int dd = (i+2)%4;
	  if(dir(grid[sy][sx])==dd){
	    grid[sy][sx] = '.';
	    if(grid[p.first][p.second]!='X')grid[p.first][p.second] = inv_dir(dd);
	    break;
	  }
	}
      }
      ans++;
      /*
      if(ans<10){
	cout << ans << endl;
	for(int i=0;i<h;i++)cout << grid[i] << endl;
	cout << endl;
      }
      */
    }
    if(ans>180)cout << "NA\n";
    else cout << ans << endl;
  }
}