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 <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"; // ↑←↓→
    int res = -1;
    REP(time, 180){
      int man = 0;
      REP(y, H)REP(x, W) if(isupper(grid[y][x])){
        man++;
        int sr = -1;
        REP(i, 4) if(NWSE[i] == grid[y][x]) sr = i;
        assert(sr != -1);
        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;
          }
        }
      }
      int dx2[4] = {-1, 0, 1, 0};
      int dy2[4] = {0, 1, 0, -1}; //←↓→↑
      const string WSEN = "WSEN"; //←↓→↑
      vector<string> n_grid = grid;
      REP(y, H)REP(x, W)REP(i, 4) if(grid[y][x] == WSEN[i]){
        int nx = x + dx2[i];
        int ny = y + dy2[i];
        if(valid(nx, ny, W, H)){
          if(n_grid[ny][nx] == '.'){
            n_grid[ny][nx] = grid[y][x];
            n_grid[y][x] = '.';
          }else if(grid[ny][nx] == '&'){
            man--;
            n_grid[y][x] = '.';
          }
        }
      }
      if(man == 0){
        res = time + 1;
        break;
      }
      grid = n_grid;
      /*
      cout << "time: " << time << endl;
      REP(y, H){
        cout << grid[y] << endl;
      }
      cout << endl;
      */
    }
    if(res == -1) cout << "NA" << endl;
    else cout << res << endl;
  }

  return 0;
}