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 <string>
#include <iomanip>
using namespace std;

int W, H, N, M;
int a[30][30];
int d[900];
int xr[900];
int xc[900];
bool x[900];

int dd[4] = {3, 0, 1, 2};
int dr[4] = {0, 1, 0, -1};
int dc[4] = {-1, 0, 1, 0};

bool input() {
  cin >> W >> H;
  if (!W && !H) {
    return false;
  }
  int id = 0;
  M = 0;
  for (int r = 0; r < H; ++r) {
    string str;
    cin >> str;
    for (int c = 0; c < W; ++c) {
      if (str[c] == '#') {
        a[r][c] = -2;
      } else if (str[c] == '.') {
        a[r][c] = 0;
      } else if (str[c] == 'X') {
        a[r][c] = -1;
        xr[M] = r;
        xc[M] = c;
        ++M;
      } else {
        a[r][c] = ++id;
        if (str[c] == 'W') {
          d[id] = 0;
        } else if (str[c] == 'S') {
          d[id] = 1;
        } else if (str[c] == 'E') {
          d[id] = 2;
        } else if (str[c] == 'N') {
          d[id] = 3;
        }
      }
    }
  }
  N = id;
  return true;
}

void solve() {
  if (!N) {
    cout << "0" << endl;
    return;
  }

  int t = 1;
  int u = 0;
  while (t <= 180) {
    for (int i = 0; i < M; ++i) {
      a[xr[i]][xc[i]] = -1;
    }
    for (int r = 0; r < H; ++r) {
      for (int c = 0; c < W; ++c) {
        if (a[r][c] <= 0) {
          continue;
        }
        int id = a[r][c];
        for (int i = 0; i < 4; ++i) {
          int nd = (d[id] + dd[i]) % 4;
          int np = a[r + dr[nd]][c + dc[nd]];
          if (!np || np == -1) {
            d[id] = nd;
            break;
          }
        }
      }
    }

    for (int i = 1; i <= N; ++i) {
      x[i] = false;
    }
    for (int i = 0; i < 4; ++i) {
      for (int r = 0; r < H; ++r) {
        for (int c = 0; c < W; ++c) {
          if (a[r][c] <= 0) {
            continue;
          }
          int id = a[r][c];
          if (d[id] != i) {
            continue;
          }
          if (x[id]) {
            continue;
          }
          x[id] = true;
          int np = a[r + dr[i]][c + dc[i]];
          if (!np) {
            a[r][c] = 0;
            a[r + dr[i]][c + dc[i]] = id;
          } else if (np == -1) {
            a[r][c] = 0;
            //a[r + dr[i]][c + dc[i]] = id;
            ++u;
          }
        }
      }
    }
    if (u == N) {
      break;
    }
    ++t;
  }
  if (t <= 180) {
    cout << t << endl;
  } else {
    cout << "NA" << endl;
  }
}

int main() {
  while (input()) {
    solve();
  }
  return 0;
}

C++: #include<iostream>

#define mp  make_pair
#define pb  push_back

using namespace std;

typedef pair<int,int> pii;

const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};

int main(){
    char board[30][31],nextboard[30][30];
    int chk[30][30];
    
    for(int w,h;cin>>w>>h,w;){
        for(int i=0;i<h;i++) cin>>board[i];
        
        int man=0;
        for(int i=0;i<h;i++)for(int j=0;j<w;j++){
            if(board[i][j]!='.' && board[i][j]!='X' && board[i][j]!='#'){
                if     (board[i][j]=='E')    board[i][j]=0;
                else if(board[i][j]=='N')    board[i][j]=1;
                else if(board[i][j]=='W')    board[i][j]=2;
                else if(board[i][j]=='S')    board[i][j]=3;
                man++;
            }
        }
        
        int ans=-1;
        for(int t=0;t<=180;t++){
            if(man==0){ ans=t; break; }
            
            for(int i=0;i<h;i++)for(int j=0;j<w;j++)  chk[i][j]=777;
            
            for(int i=0;i<h;i++)for(int j=0;j<w;j++){
                if(board[i][j]>3) continue;
                for(int k=0,l=(board[i][j]+3)%4;k<4;k++,l=(l+1)%4){
                    int y=i+dy[l],x=j+dx[l];
                    if(0<=y && y<h && 0<=x && x<w && (board[y][x]=='.' || board[y][x]=='X')){
                        board[i][j]=l;
                        chk[y][x]=min(chk[y][x],(l+2)%4);
                        break;
                    }
                }
            }
            
            for(int i=0;i<h;i++)for(int j=0;j<w;j++)  nextboard[i][j]=board[i][j];
            
            for(int i=0;i<h;i++)for(int j=0;j<w;j++){
                if(board[i][j]>3) continue;
                int y=i+dy[board[i][j]],x=j+dx[board[i][j]];
                if(0<=y && y<h && 0<=x && x<w && chk[y][x]==(board[i][j]+2)%4){ 
                    if(board[y][x]=='.') nextboard[y][x]=board[i][j];
                    else if(board[y][x]=='X')    man--;
                    else{while(1);}
                    nextboard[i][j]='.';
                }
            }
            for(int i=0;i<h;i++)for(int j=0;j<w;j++)  board[i][j]=nextboard[i][j];
        }
        
        if(ans >= 0)    cout<<ans<<endl;
        else        cout<<"NA"<<endl;
    }
    
    return 0;
}