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>
#include<algorithm>
using namespace std;

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

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;
                index = (index - 1 + 4) % 4;
                for(int k = 0; k < 5; ++k) {
                    int y = i + Next[index][0];
                    int x = j + Next[index][1];
                    if(field[y][x] == '.' || field[y][x] == 'X') break;
                    index = (index + 1) % 4;
                }
                field[i][j] = Direction[index];
            }
            // 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][0];
                    int x = j + Next[d][1];
                    if(y < 0 || h <= y) continue;
                    if(x < 0 || w <= x) continue;
                    int index = Direction.find(field[y][x]);
                    if(index == string::npos) continue;
                    if((index - d + 4) % 4 != 2) continue;
                    if(used[y][x]) continue;
                    used[i][j] = 1;
                    if(field[i][j] == '.') swap(field[i][j], field[y][x]);
                    else field[y][x] = '.';
                    break;
                }
            }
        }

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

C++: // 2011/08/05 Tazoe

#include <iostream>
using namespace std;

struct man{
	int x;
	int y;
	int d;
};

int main()
{
	while(true){
		int W, H;
		cin >> W >> H;
		if(W==0&&H==0)
			break;

		char S[30][30];
		struct man M[900];
		int N = 0;
		for(int y=0; y<H; y++){
			for(int x=0; x<W; x++){
				cin >> S[y][x];

				if(S[y][x]=='E'||S[y][x]=='N'||S[y][x]=='W'||S[y][x]=='S'){
					M[N].x = x;
					M[N].y = y;
					if(S[y][x]=='E')
						M[N].d = 2;
					else if(S[y][x]=='N')
						M[N].d = 3;
					else if(S[y][x]=='W')
						M[N].d = 0;
					else if(S[y][x]=='S')
						M[N].d = 1;
					N++;
					S[y][x] = '@';
				}
			}
		}

		bool flg = false;
		for(int t=1; t<=180; t++){
			for(int i=0; i<N; i++){
				int D = (M[i].d+4-1)%4;
				for(int j=0; j<4; j++){
					if(D==2&&(S[M[i].y][M[i].x+1]=='.'||S[M[i].y][M[i].x+1]=='X'))
						break;
					else if(D==3&&(S[M[i].y-1][M[i].x]=='.'||S[M[i].y-1][M[i].x]=='X'))
						break;
					else if(D==0&&(S[M[i].y][M[i].x-1]=='.'||S[M[i].y][M[i].x-1]=='X'))
						break;
					else if(D==1&&(S[M[i].y+1][M[i].x]=='.'||S[M[i].y+1][M[i].x]=='X'))
						break;
					D = (D+1)%4;
				}
				M[i].d = D;
			}

			for(int i=0; i<N-1; i++)
				for(int j=i+1; j<N; j++)
					if(M[i].d>M[j].d){
						struct man tmp = M[i];
						M[i] = M[j];
						M[j] = tmp;
					}

			for(int i=0; i<N; i++)
				if(M[i].d==2&&S[M[i].y][M[i].x+1]!='@'){
					if(S[M[i].y][M[i].x+1]=='X')
						M[i].d = 9;
					S[M[i].y][M[i].x] = '.';
					M[i].x += 1;
					S[M[i].y][M[i].x] = '@';
				}
				else if(M[i].d==3&&S[M[i].y-1][M[i].x]!='@'){
					if(S[M[i].y-1][M[i].x]=='X')
						M[i].d = 9;
					S[M[i].y][M[i].x] = '.';
					M[i].y -= 1;
					S[M[i].y][M[i].x] = '@';
				}
				else if(M[i].d==0&&S[M[i].y][M[i].x-1]!='@'){
					if(S[M[i].y][M[i].x-1]=='X')
						M[i].d = 9;
					S[M[i].y][M[i].x] = '.';
					M[i].x -= 1;
					S[M[i].y][M[i].x] = '@';
				}
				else if(M[i].d==1&&S[M[i].y+1][M[i].x]!='@'){
					if(S[M[i].y+1][M[i].x]=='X')
						M[i].d = 9;
					S[M[i].y][M[i].x] = '.';
					M[i].y += 1;
					S[M[i].y][M[i].x] = '@';
				}

			for(int i=0; i<N; i++)
				if(M[i].d==9)
					S[M[i].y][M[i].x] = 'X';

			for(int i=0; i<N-1; i++)
				for(int j=i+1; j<N; j++)
					if(M[i].d>M[j].d){
						struct man tmp = M[i];
						M[i] = M[j];
						M[j] = tmp;
					}

			for(int i=0; i<N; i++)
				if(M[i].d==9){
					N = i;
					break;
				}

/*
			char S2[30][30];
			for(int y=0; y<H; y++)
				for(int x=0; x<W; x++)
					S2[y][x] = S[y][x];

			for(int i=0; i<N; i++)
				if(M[i].d==2)
					S2[M[i].y][M[i].x] = 'E';
				else if(M[i].d==3)
					S2[M[i].y][M[i].x] = 'N';
				else if(M[i].d==0)
					S2[M[i].y][M[i].x] = 'W';
				else if(M[i].d==1)
					S2[M[i].y][M[i].x] = 'S';

			for(int y=0; y<H; y++){
				for(int x=0; x<W; x++)
					cout << S2[y][x];
				cout << endl;
			}
*/

			if(N==0){
				cout << t << endl;
				flg = true;
				break;
			}
		}

		if(!flg)
			cout << "NA" << endl;
	}

	return 0;
}