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 <map>
#include <cstdlib>
#include <algorithm>
#include <string>

using namespace std;

const int N = 30;

int h, w;
char data[N][N], next[N][N];
int dy[] = {0, -1, 0, 1};
int dx[] = {1, 0, -1, 0};
map<char, int> ctoi;
string itoc = "ENWS";

void copy(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         data[i][j] = next[i][j];
      }
   }
}

bool check(int a, int b){
   if(a == 0 && b == 2) return true;
   if(a == 2 && b == 0) return true;
   if(a == 1 && b == 3) return true;
   if(a == 3 && b == 1) return true;
   return false;
}

main(){
   ctoi['E'] = 0;
   ctoi['N'] = 1;
   ctoi['W'] = 2;
   ctoi['S'] = 3;
   while(cin >> w >> h && (h || w)){
      int p = 0;
      for(int i=0;i<h;++i){
         for(int j=0;j<w;++j){
            cin >> next[i][j];
            if(next[i][j] == 'E' ||
               next[i][j] == 'N' ||
               next[i][j] == 'W' ||
               next[i][j] == 'S') ++p;
         }
      }
      copy();
      int t;
      for(t=0;t<=180;++t){
         if(p == 0) break;
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '#' ||
                  data[i][j] == '.' ||
                  data[i][j] == 'X') continue;
               for(int k=0;k<4;++k){
                  int d = (ctoi[data[i][j]] + 3 + k) % 4;
                  int ty = i + dy[d];
                  int tx = j + dx[d];
                  if(ty<0 || ty>=h) continue;
                  if(tx<0 || tx>=w) continue;
                  if(data[ty][tx] == '.' || data[ty][tx] == 'X'){
                     data[i][j] = itoc[d];
                     break;
                  }
               }
            }
         }
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '.' || data[i][j] == 'X'){
                  for(int k=0;k<4;++k){
                     int ty = i + dy[k];
                     int tx = j + dx[k];
                     if(ty<0 || ty>=h) continue;
                     if(tx<0 || tx>=w) continue;
                     if(data[ty][tx] == '#' ||
                        data[ty][tx] == '.' ||
                        data[ty][tx] == 'X') continue;
                     if(check(ctoi[data[ty][tx]], k)){
                        //if(abs(ctoi[data[ty][tx]] - k) == 2){
                        if(data[i][j] == 'X') --p;
                        else next[i][j] = data[ty][tx];
                        next[ty][tx] = '.';
                        break;
                     }
                  }
               }
            }
         }
         copy();
      }
      if(t > 180) cout << "NA" << endl;
      else cout << t << endl;
   }
   return 0;
}

C++: #include <iostream>
#include <map>
#include <cstdlib>
#include <algorithm>
#include <string>

using namespace std;

const int N = 30;

int h, w, t, p;
char data[N][N], next[N][N];
int dy[] = {0, -1, 0, 1};
int dx[] = {1, 0, -1, 0};
map<char, int> ctoi;
string itoc = "ENWS";

void copy(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         data[i][j] = next[i][j];
      }
   }
}

main(){
   ctoi['E'] = 0;
   ctoi['N'] = 1;
   ctoi['W'] = 2;
   ctoi['S'] = 3;
   while(cin >> w >> h && (h || w)){
      fill(next[0], next[N], '#');
      p = 0;
      for(int i=0;i<h;++i){
         for(int j=0;j<w;++j){
            cin >> next[i][j];
            if(next[i][j] == 'E' ||
               next[i][j] == 'N' ||
               next[i][j] == 'W' ||
               next[i][j] == 'S') ++p;
         }
      }
      h = w = N;
      copy();
      for(t=0;t<=180;++t){
         if(p == 0) break;
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '#' ||
                  data[i][j] == '.' ||
                  data[i][j] == 'X') continue;
               for(int k=0;k<4;++k){
                  int d = (ctoi[data[i][j]] + 3 + k) % 4;
                  int ty = i + dy[d];
                  int tx = j + dx[d];
                  if(ty<0 || ty>=h) continue;
                  if(tx<0 || tx>=w) continue;
                  if(data[ty][tx] == '.' || data[ty][tx] == 'X'){
                     data[i][j] = itoc[d];
                     break;
                  }
               }
            }
         }
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '.' || data[i][j] == 'X'){
                  for(int k=0;k<4;++k){
                     int ty = i + dy[k];
                     int tx = j + dx[k];
                     if(ty<0 || ty>=h) continue;
                     if(tx<0 || tx>=w) continue;
                     if(data[ty][tx] == '#' ||
                        data[ty][tx] == '.' ||
                        data[ty][tx] == 'X') continue;
                        if(abs(ctoi[data[ty][tx]] - k) == 2){
                        if(data[i][j] == 'X') --p;
                        else next[i][j] = data[ty][tx];
                        next[ty][tx] = '.';
                        break;
                     }
                  }
               }
            }
         }
         copy();
      }
      if(t > 180) cout << "NA" << endl;
      else cout << t << endl;
   }
   return 0;
}