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>
using namespace std;
int dy[]={-1,0,1,0};
int dx[]={0,1,0,-1};
bool isEmpty(char ch){
  if(ch=='.'||ch=='X')return true;
  else return false;
}
int change(char ch){
  if(ch=='N')return 0;
  if(ch=='E')return 1;
  if(ch=='S')return 2;
  if(ch=='W')return 3;
  return -1;
}
char change2(int x){
  if(x==0)return 'N';
  if(x==1)return 'E';
  if(x==2)return 'S';
  if(x==3)return 'W';
  return '-';
}
char t[30][30],tmp[30][30];
int W,H;
 
int main(){
  while(1){
    cin>>W>>H;
    if(W==0&&H==0)break;
    for(int i=0;i<H;i++)
      for(int j=0;j<W;j++)
    cin>>t[i][j];
    int ans=0;
    while(1){
      ///////////////////////////////////////////////
      bool flag=false;
      for(int i=0;i<H;i++){
	for(int j=0;j<W;j++){
	  if(change(t[i][j])==-1)continue;
	  flag=true;
	  int dir=change(t[i][j]);
	  for(int k=5;k>=2;k--){
	    int ndir=(dir+k)%4;
	    int ny=i+dy[ndir],nx=j+dx[ndir];
	    if(t[ny][nx]=='.'||t[ny][nx]=='X'){
	      t[i][j]=change2(ndir);
	      break;
	    }
	  }//k
	}//j
      }//i
      if(flag==false)break;
      ///////////////////////////////////////////////
      ans++;
      if(ans>180)break;
      /////////////////////////////////////////////// w s e n
      
      for(int i=0;i<H;i++){
	for(int j=0;j<W;j++){
	  if(change(t[i][j])==-1){
	    tmp[i][j]=t[i][j];
	  }else tmp[i][j]='.';
	}
      }
      
      for(int k=3;k>=0;k--){
	for(int i=0;i<H;i++){
	  for(int j=0;j<W;j++){
	    if(k!=change(t[i][j]))continue;
	    int ny=i+dy[k],nx=j+dx[k];
	    if(isEmpty(t[ny][nx])&&isEmpty(tmp[ny][nx])){
	      if(tmp[ny][nx]=='.')tmp[ny][nx]=t[i][j];
	    }else{
	      tmp[i][j]=t[i][j];
	    }
	  }
	}
      }
      
      for(int i=0;i<H;i++){
	for(int j=0;j<W;j++){
	  t[i][j]=tmp[i][j];
	}
      }
      ///////////////////////////////////////////////
      
    }
    if(ans>180)cout<<"NA"<<endl;
    else cout<<ans<<endl;
  }
  return 0;
}

C++: #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>

using namespace std;

#ifdef _MSC_VER
#define __typeof__ decltype

template <class T>
int __builtin_popcount(T n) { return n ? 1 + __builtin_popcount(n & (n - 1)) : 0; }
#endif

#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define popcount __builtin_popcount

const double EPS = 1e-8;
typedef long long ll;
typedef pair<int, int> pint;


int main()
{
	int W, H;
	int dx[] = { 1, 0, -1, 0 };
	int dy[] = { 0, -1, 0, 1 };
	char* dirs = "ENWS";

	while (scanf("%d%d", &W, &H), W | H)
	{
		char maze[64][64];
		for (int i = 0; i < H; ++i)
			scanf("%s", maze + i);

		int time;
		for (time = 0; time <= 180; ++time)
		{
			bool any = false;
			bool mark[64][64];
			memset(mark, 0, sizeof(mark));
			for (int i = 0; i < H; ++i)
			{
				for (int j = 0; j < W; ++j)
				{
					char* hoge = strchr(dirs, maze[i][j]);
					if (!hoge)
						continue;

					any = true;

					int dir = hoge - dirs;
					int next_dir = -1;
					for (int k = -1; k < 3; ++k)
					{
						int d = (dir + k + 4) % 4;
						int tx = j + dx[d];
						int ty = i + dy[d];
						if (tx < 0 || ty < 0 || tx >= W || ty >= H)
							continue;

						char c = maze[ty][tx];
						if (c == '.' || c == 'X')
						{
							next_dir = d;
							break;
						}
					}
					if (next_dir != -1)
					{
						maze[i][j] = dirs[next_dir];
						mark[i+dy[next_dir]][j+dx[next_dir]] = true;
					}
				}
			}
			if (!any)
				break;

			for (int i = 0; i < H; ++i)
			{
				for (int j = 0; j < W; ++j)
				{
					if (!mark[i][j])
						continue;

					int k;
					int tx, ty;
					for (k = 0; k < 4; ++k)
					{
						tx = j + dx[k];
						ty = i + dy[k];
						char* pp;
						if (tx >= 0 && ty >= 0 && tx < W && ty < H
							&& (pp = strchr(dirs, maze[i+dy[k]][j+dx[k]])) != NULL
							&& pp - dirs < 4 && maze[ty][tx] == dirs[(k+2)%4])
						{
							if (maze[i][j] == '.')
								maze[i][j] = maze[ty][tx];
							break;
						}
					}
					maze[ty][tx] = '.';
				}
			}
		}
		if (time == 0)
			puts("1");
		else if (time != 181)
			printf("%d\n", time);
		else
			puts("NA");
	}

	return 0;
}