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 <bits/stdc++.h>
 
using namespace std;
 
#define MAX 35
typedef vector<char> Vec;
typedef vector<Vec> Mat;
 
struct Person {
    int x, y, d;
    Person(){}
    Person(int x, int y, int d)
        : x(x), y(y), d(d) {}
};
 
int W, H;
vector<Person> v;
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, -1, 0, 1};
 
bool inField(int x, int y)
{
    return (0 <= x && x < W && 0 <= y && y < H);
}
 
int getD(int d, int x)
{
    int v[] = {1, 0, 3, 2};
    return (v[(x-d+4)%4]);
}
 
void solve(Mat &maze)
{
    for (int T = 0; T < 180; T++) {
        int N = v.size();
        vector<Person> v2(N), v3 = v;
        int cnt[MAX][MAX] = {{}}, num[MAX][MAX];
        memset(num, -1, sizeof(num));
 
        for (int i = 0; i < N; i++) {
            int d = (4 - v[i].d) % 4;
            for (int j = 0; j < 4; j++) {
                int nd = (d + j) % 4;
                int nx = v[i].x + dx[nd];
                int ny = v[i].y + dy[nd];
                if (maze[ny][nx] == '.' || maze[ny][nx] == 'X') {
                    cnt[ny][nx]++;
                    num[v[i].y][v[i].x] = i;
                    v2[i] = Person(nx,ny,getD(v[i].d,j));
                    v3[i].d = getD(v[i].d,j);
                    break;
                }
            }
        }
        v.clear();
        bool used[MAX*MAX] = {0};
        const int dx2[] = {1, 0, -1, 0};
        const int dy2[] = {0, -1, 0, 1};
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                if (cnt[i][j] == 0) continue;
                for (int k = 0; k < 4; k++) {
                    int nx = j + dx2[k];
                    int ny = i + dy2[k];
                    int idx = num[ny][nx];
                    if (!inField(nx, ny)) continue;
                    if (i != v2[idx].y ||
                       j != v2[idx].x) continue;
                     
                    if (idx != -1) {
                        maze[ny][nx] = '.';
                        if (maze[i][j] == '.') {
                            maze[i][j] = '*';
                            v.push_back(v2[idx]);
                        }
                        used[idx] = 1;
                        break;
                    }
                }
            }
        }
        for (int i = 0; i < N; i++) {
            if (!used[i]) {
                v.push_back(v3[i]);
            }
        }
        if (v.size() == 0) {
            cout << T+1 << endl;
            return;
        }
    }
    cout << "NA" << endl;
}
 
int main()
{
    while (cin >> W >> H, W) {
        Mat maze(H, Vec(W));
        v.clear();
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                cin >> maze[i][j];
                if (maze[i][j] == 'N') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 0));
                } else if (maze[i][j] == 'E') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 1));
                } else if (maze[i][j] == 'S') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 2));
                } else if (maze[i][j] == 'W') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 3));
                }
            }
        }
        solve(maze);
    }
    return 0;
}