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 <vector>
#include <string>
using namespace std;

int dx[] = {1,0,-1,0};
int dy[] = {0,-1,0,1};
int H, W;

int foo(char c) {
	switch(c) {
		case 'N' : return 0;
		case 'W' : return 1;
		case 'S' : return 2;
		case 'E' : return 3;
	}
	return -1;
}

char bar(int d) {
	switch(d) {
		case 0 : return 'E';
		case 1 : return 'N';
		case 2 : return 'W';
		case 3 : return 'S';
	}
}

bool is_valid(int y, int x) {
	return 0 <= y && y < H && 0 <= x && x < W;
}

int main() {
	while(cin >> W >> H, W || H) {
		vector<string> m;
		for(int i = 0; i < H; i++) {
			string s;
			cin >> s;
			m.push_back(s);
		}

		int ret = 0;
		for(int t = 0; t < 180; t++) {
			vector<string> next;
			for(int i = 0; i < m.size(); i++) {
				string s = "";
				for(int j = 0; j < m[i].size(); j++) {
					if(foo(m[i][j]) != -1)
						s += ".";
					else
						s += m[i][j];
				}
				next.push_back(s);
			}

			for(int i = 0; i < m.size(); i++) {
				for(int j = 0; j < m[i].size(); j++) {
					if(foo(m[i][j]) != -1) {
						ret = t;
						for(int k = 0; k < 4; k++) {
							int x, y;
							y = i+dy[(k+foo(m[i][j]))%4];
							x = j+dx[(k+foo(m[i][j]))%4];
							if(is_valid(y,x) && m[y][x] == 'X') {
								break;
							}
							else if(is_valid(y,x) && m[y][x] == '.' && next[y][x] == '.') {
								next[y][x] = bar((k+foo(m[i][j])) % 4);
								break;
							}
							else if(is_valid(y,x) && m[y][x] == '.' && next[y][x] != '.') {
								next[i][j] = m[i][j];
								break;
							}
						}
					}
				}

			}

			m = next;

/*
			for(int j = 0; j < m[i].size(); j++) {
				cout << next[i][j];
				cout << endl;
			}
			cout << endl;
// */
		}

		for(int i = 0; i < m.size(); i++) {
			for(int j = 0; j < m[i].size(); j++) {
				if(foo(m[i][j]) != -1)
					ret = -1;
			}
		}

		if(ret == -1)
			cout << "NA" << endl;
		else
			cout << ret + 1 << endl;
	}
}

/*
 *
 * ICPC challenge club 2014 年忘年会
 * 金土日の方が都合がよい
 * SRMは外す
 * SRM 12/07 02:00~
 * SRM 12/12 01:00~
 * SRM 12/16 11:00~
 *
 * SRMは外す
 * 顧問の先生の参加はぜひ
 *
 * 予算3000円くらい
 *
 * 12/15以降がよい
 * 12月中
 *
 * 九州大学ICPCチャレンジ部部員募集中です
 */

C++: #include <iostream>
#include <sstream>
#include <string>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cassert>

using namespace std;

#define FOR(i,k,n) for(int i=(k); i<(int)(n); ++i)
#define REP(i,n) FOR(i,0,n)
#define FORIT(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)

template<class T> void debug(T begin, T end){ for(T i = begin; i != end; ++i) cerr<<*i<<" "; cerr<<endl; }
inline bool valid(int x, int y, int W, int H){ return (x >= 0 && y >= 0 && x < W && y < H); }

typedef long long ll;
const int INF = 100000000;
const double EPS = 1e-8;
const int MOD = 1000000007;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, -1, 0, 1};

int main(){
  int W, H;
  while(cin>>W>>H && W){
    vector<string> grid(H);
    REP(i, H) cin >> grid[i];
    REP(y, H) REP(x, W) if(grid[y][x] == 'X') grid[y][x] = '&';
    const string NWSE = "NWSE";
    const string WSEN = "WSEN";
    REP(time, 182){
      bool gameover = true;
      REP(y, H)REP(x, W) if(isupper(grid[y][x])){
        gameover = false;
        int sr = -1;
        REP(i, 4) if(NWSE[i] == grid[y][x]) sr = i;
        REP(dr, 4){
          int r = (sr + dr) % 4;
          int nx = x + dx[r];
          int ny = y + dy[r];
          if(valid(nx, ny, W, H) && (grid[ny][nx] == '.' || grid[ny][nx] == '&')){
            grid[y][x] = NWSE[(r + 3) % 4];
            break;
          }
        }
      }
      if(time >= 181){
        cout << "NA" << endl;
        break;
      }
      if(gameover){
        cout << time << endl;
        break;
      }
      int dx2[4] = {-1, 0, 1, 0};
      int dy2[4] = {0, 1, 0, -1};
      bool used[30][30] = {};
      REP(y, H)REP(x, W)REP(i, 4) if(grid[y][x] == WSEN[i] && !used[y][x]){
        int nx = x + dx2[i];
        int ny = y + dy2[i];
        if(valid(nx, ny, W, H) && !used[ny][nx]){
          used[ny][nx] = true;
          if(grid[ny][nx] == '.'){
            grid[ny][nx] = grid[y][x];
            grid[y][x] = '.';
          }else if(grid[ny][nx] == '&'){
            grid[y][x] = '.';
          }
        }
      }
      /*
      cout << "time: " << time << endl;
      REP(y, H){
        cout << grid[y] << endl;
      }
      cout << endl;
      */
    }
  }

  return 0;
}