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] = {{0}};
        int 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;
}

C++: #include<stdio.h>
#include<string.h>
#include<vector>
int dx[]={-1,0,1,0},dy[]={0,1,0,-1};
struct S{int x,y,a;S(int x,int y,int a):x(x),y(y),a(a){}};
int F(char c){return c=='.'||c=='X';}
int main()
{
	char*p,a[32][32];
	int W,H,x,y,t,i,j;
	while(scanf("%d%d",&W,&H),W)
	{
		std::vector<S>v,u[4],g,b;
		for(y=0;y<H;++y)
		{
			scanf("%s",a[y]);
			for(p=a[y];p=strpbrk(p,"NEWS");++p)
				v.push_back(S(p-a[y],y,*p=='W'?0:*p=='S'?1:*p=='E'?2:3));
		}
		for(t=0;t<181&&v.size();++t)
		{
			for(i=0;i<4;++i)u[i].clear();
			b.clear();
			for(i=0;i<v.size();++i)
			{
				S s=v[i];
				for(j=0;j<4;++j)
				{
					x=s.x+dx[(s.a+3+j)%4];
					y=s.y+dy[(s.a+3+j)%4];
					if(F(a[y][x]))
					{
						s.a=(s.a+3+j)%4;
						u[s.a].push_back(s);
						goto N;
					}
				}
				b.push_back(s);
				N:;
			}
			v=b;
			g.clear();
			for(i=0;i<4;++i)
			{
				for(j=0;j<u[i].size();++j)
				{
					S s=u[i][j];
					x=s.x+dx[i];
					y=s.y+dy[i];
					if(F(a[y][x]))
					{
						a[s.y][s.x]='.';
						s.x=x;
						s.y=y;
						if(a[y][x]=='X')
						{
							g.push_back(s);
							a[y][x]='@';
							continue;
						}
						a[y][x]='@';
					}
					v.push_back(s);
				}
			}
			for(i=0;i<g.size();++i)a[g[i].y][g[i].x]='X';
		}
		if(t<181)printf("%d\n",t);
		else puts("NA");
	}
	return 0;
}