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 <stdio.h>

using namespace std;

void move( char stage[31][31], int y, int x, int dy, int dx ){
	if( stage[dy][dx] == 'X' ) stage[y][x] = '.';
	else if( stage[dy][dx] == '.' ){ stage[dy][dx] = stage[y][x] - 'A'; stage[y][x] = '.'; }
}
bool check( char stage[31][31], int y, int x ){
	return stage[y][x] == '.' || stage[y][x] == 'X';
}

void unitE( char stage[31][31], int y, int x )
{
	if( check(stage, y + 1, x ) ) stage[y][x] = 'S';
	else if( check(stage, y , x + 1 ) ) stage[y][x] = 'E';
	else if( check(stage, y - 1, x ) ) stage[y][x] = 'N';
	else if( check(stage, y, x - 1 ) ) stage[y][x] = 'W';
}
void unitW( char stage[31][31], int y, int x )
{
	if( check(stage, y - 1, x ) ) stage[y][x] = 'N';
	else if( check(stage, y , x - 1 ) ) stage[y][x] = 'W';
	else if( check(stage, y + 1, x ) ) stage[y][x] = 'S';
	else if( check(stage, y, x + 1 ) ) stage[y][x] = 'E';
}
void unitS( char stage[31][31], int y, int x )
{
	if( check(stage, y, x - 1 ) ) stage[y][x] = 'W';
	else if( check(stage, y + 1 , x ) ) stage[y][x] = 'S';
	else if( check(stage, y, x + 1) ) stage[y][x] = 'E';
	else if( check(stage, y - 1, x ) ) stage[y][x] = 'N';
}
void unitN( char stage[31][31], int y, int x )
{
	if( check(stage, y, x + 1 ) ) stage[y][x] = 'E';
	else if( check(stage, y - 1 , x ) ) stage[y][x] = 'N';
	else if( check(stage, y, x - 1) ) stage[y][x] = 'W';
	else if( check(stage, y + 1, x ) ) stage[y][x] = 'S';
}
int main(int argc, char const* argv[])
{
	char stage[31][31];
	int w,h,t;

	while( cin >> w >> h && w ){
		t = 180;
		for( int i = 0;i < 31;i++ ){
			for( int j = 0;j < 31;j++ ){
				stage[i][j] = 0;
			}
		}

		for( int i = 0;i < h;i++ ){
			cin >> stage[i];
		}

		for( t = 0;t < 180;t++ ){
			int count = 0;
			for( int i = 0;i < h;i++ ){
				for( int j = 0;j < w;j++ ){
					if( stage[i][j] == 'E' ){ unitE( stage, i, j ); count++;}
					else if( stage[i][j] == 'N' ){ unitN( stage, i, j ); count++;}
					else if( stage[i][j] == 'W' ){ unitW( stage, i, j ); count++;}
					else if( stage[i][j] == 'S' ){ unitS( stage, i, j ); count++;}
				}
			}
			if( count == 0 ){ cout << t << endl; break; }
			for( int i = 0;i < h;i++ ){
				for( int j = 0;j < w;j++ ){
					if( stage[i][j] == '.' || stage[i][j] == 'X' ){
						if( stage[i][j + 1] == 'W' ) move( stage, i, j+1, i, j );
						else if( stage[i - 1][j] == 'S' ) move( stage, i - 1,j , i, j );
						else if( stage[i][j - 1] == 'E' ) move( stage, i, j - 1,i , j );
						else if( stage[i + 1][j] == 'N' ) move( stage, i + 1,j, i, j );
					}
				}
			}
			for( int i = 0;i < h;i++ ){
				for( int j = 0;j < w;j++ ){
					int target = stage[i][j] + 'A';
					if( target == 'E' || target == 'W' || target == 'S' || target == 'N' ) stage[i][j] += 'A';
				}
			}
		}
		if( t == 180 ) cout << "NA" << endl;

	}
	return 0;
}