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>
using namespace std;

const string Direction = {"ENWS"};
const int Next[4][2] = {{0, 1}, {-1, 0}, {0, -1}, {1, 0}};
enum {Y, X};

int main() {
    int w, h;
    while(cin >> w >> h, w | h) {
        int time;
        vector<string> field(h);
        for(int i = 0; i < h; ++i) cin >> field[i];

        for(time = 0; time <= 180; ++time) {
            bool ok = true;
            for(const auto& line: field) for(const auto& c: line)
                if(Direction.find(c) != string::npos) ok = false;
            if(ok) break;
            // turn
            for(int i = 0; i < h; ++i) for(int j = 0; j < w; ++j) {
                int index = Direction.find(field[i][j]);
                if(index == string::npos) continue;
                for(int k = 0; k < 4; ++k) {
                    int d = (index + 3 + k) % 4;
                    int y = i + Next[d][Y];
                    int x = j + Next[d][X];
                    if(field[y][x] != '.' && field[y][x] != 'X') continue;
                    field[i][j] = Direction[d];
                    break;
                }
            }
            // move
            vector<vector<int>> used(h, vector<int>(w, 0));
            for(int i = 0; i < h; ++i) for(int j = 0; j < w; ++j) {
                if(field[i][j] != '.' && field[i][j] != 'X') continue;
                for(int d = 0; d < 4; ++d) {
                    int y = i + Next[d][Y];
                    int x = j + Next[d][X];
                    if(y < 0 || h <= y) continue;
                    if(x < 0 || w <= x) continue;
                    if(field[y][x] != Direction[(d + 2) % 4]) continue;
                    if(used[y][x]) continue;
                    used[i][j] = 1;
                    if(field[i][j] == '.') field[i][j] = field[y][x];
                    field[y][x] = '.';
                    break;
                }
            }
        }

        if(time > 180) cout << "NA" << endl;
        else cout << time << endl;
    }
}

C++: #include<iostream>
#include<vector>
#include<string>
#include<algorithm>
#include<map>
#include<set>
#include<utility>
#include<cmath>
#include<cstring>
#include<queue>
#include<cstdio>
#include<sstream>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define pb push_back
#define mp make_pair
#define all(in) in.begin(),in.end()
const double PI=acos(-1);
const double EPS=1e-8;
const int inf=1e9;
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;
int main(){
	int dx[]={0,1,0,-1,0,1,0,-1};
	int dy[]={-1,0,1,0,-1,0,1,0};
	int n,m;
	while(cin>>m>>n,n+m){
		vector<string>in(n);
		rep(i,n)cin>>in[i];
		map<int,map<int,bool> >ma;
		rep(i,n)rep(j,m)if(in[i][j]=='X')ma[i][j]=true;
		rep(i,n)rep(j,m)if(in[i][j]=='N')in[i][j]='2';
		else if(in[i][j]=='E')in[i][j]='1';
		else if(in[i][j]=='S')in[i][j]='0';
		else if(in[i][j]=='W')in[i][j]='3';
		int c=0;
		rep(i,n)rep(j,m)if(isdigit(in[i][j]))c++;
		rep(q,181){
//			cout<<q<<endl;
			if(q==180){
				cout<<"NA"<<endl;
				break;
			}
			vvi tmp(n,vi(m));
			rep(i,n)rep(j,m)if(isdigit(in[i][j])){
				int t=in[i][j]-'0';
				rep(k,4)if(in[i+dx[t+k]][j+dy[t+k]]!='#'&&
					!isdigit(in[i+dx[t+k]][j+dy[t+k]])){
					tmp[i][j]=(t+k)%4+1;
					break;
				}
			}
//			rep(i,n){rep(j,m)cout<<" "<<tmp[i][j];cout<<endl;}
			rep(k,4){
				rep(i,n)rep(j,m)if(tmp[i][j]==k+1){
					if(!isdigit(in[i+dx[k]][j+dy[k]])){
//						cout<<i+dx[k]<<" "<<j+dy[k]<<endl;
						in[i+dx[k]][j+dy[k]]=(tmp[i][j]+2)%4+'0';
						in[i][j]='.';
					}
				}
			}
//			rep(i,n)cout<<in[i]<<endl;cout<<endl;
			rep(i,n)rep(j,m)if(isdigit(in[i][j])&&ma[i][j]){
				c--;
				if(!c){
					cout<<q+1<<endl;
					goto end;
				}
				in[i][j]='X';
			}
//			rep(i,n)cout<<in[i]<<endl;cout<<endl;
		}
		end:;
	}
}