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>
using namespace std;

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

int main()
{
	int W,H;
	while(cin >> W >> H, (W||H))
	{
		int cnt=0, p[35][35],tp[35][35];
		char f[35][35];
		cin.ignore();
		for(int i=0; i<H; i++)
		{
			string t;
			getline(cin, t);
			for(int j=0; j<W; j++)
			{
				f[j][i]=t[j];
				p[j][i]=-1;
				if(f[j][i]=='E') p[j][i]=0;
				if(f[j][i]=='S') p[j][i]=3;
				if(f[j][i]=='W') p[j][i]=2;
				if(f[j][i]=='N') p[j][i]=1;
				
				if(p[j][i]!=-1) cnt++;
			}
		}
		
		int ret=0;
		for(; ret<=180; ret++)
		{
			if(cnt==0) break;
			
			for(int i=0; i<H; i++)
			for(int j=0; j<W; j++)
			{
				tp[j][i]=-1;
				
				if(p[j][i]!=-1)
				{
					int next=p[j][i];
					for(int k=0; k<4; k++)
					{
						int d=(p[j][i]+k+3)%4;
						int tx=j+dx[d], ty=i+dy[d];
						if(tx<0||ty<0||tx>=W||ty>=H) continue;
						if(f[tx][ty]=='#'||p[tx][ty]!=-1) continue;
						
						next=d;
						break;
					}
					
					p[j][i]=next;
				}
			}
			
			for(int i=0; i<H; i++)
			for(int j=W-1; j>=0; j--)
			{
				if(p[j][i]!=-1)
				{
					int tx=j+dx[p[j][i]], ty=i+dy[p[j][i]];
					if(tp[tx][ty]==-1&&p[tx][ty]==-1) tp[tx][ty]=p[j][i];
					else tp[j][i]=p[j][i];
				}
			}
			
			memcpy(p, tp, sizeof(p));
			
			for(int i=0; i<H; i++)
			for(int j=0; j<W; j++)
			{
				if(f[j][i]=='X'&&p[j][i]!=-1)
				{
					cnt--;
					p[j][i]=-1;
				}
			}
		}
		
		if(ret>180) cout <<"NA"<< endl;
		else cout << ret << endl;
	}
}

C++: #include <iostream>
#include <string>
#include <iomanip>
using namespace std;

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

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

void print_map() {
  for (int r = 0; r < H; ++r) {
    for (int c = 0; c < W; ++c) {
      char q = 0;
      if (a[r][c] == 0) {
        q = '.';
      } else if (a[r][c] == -1) {
        q = 'X';
      } else if (a[r][c] == -2) {
        q = '#';
      } else {
        int x = d[a[r][c]];
        if (!x) {
          q = 'W';
        } else if (x == 1) {
          q = 'S';
        } else if (x == 2) {
          q = 'E';
        } else if (x == 3) {
          q = 'N';
        }
      }
      cout << setw(3) << q;
    }
    cout << endl;
  }
  cout << endl;
}

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;
        pr[id] = r;
        pc[id] = c;
        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;
  for (int id = 1; id <= N; ++id) {
    y[id] = false;
  }
  while (t <= 180) {
    for (int id = 1; id <= N; ++id) {
      if (y[id]) {
        continue;
      }
      int r = pr[id];
      int c = pc[id];
      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 r = 0; r < H; ++r) {
      for (int c = 0; c < W; ++c) {
        b[r][c] = 0;
      }
    }
    for (int id = 1; id <= N; ++id) {
      x[id] = false;
    }
    for (int i = 0; i < 4; ++i) {
      for (int id = 1; id <= N; ++id) {
        if (y[id]) {
          continue;
        }
        int r = pr[id];
        int c = pc[id];
        if (d[id] != i) {
          continue;
        }
        int np = a[r + dr[i]][c + dc[i]];
        if ((!np || np == -1) && !b[r + dr[i]][c + dc[i]]) {
          b[r + dr[i]][c + dc[i]] = id;
          x[id] = true;
        }
      }
    }

    for (int id = 1; id <= N; ++id) {
      if (y[id]) {
        continue;
      }
      int r = pr[id];
      int c = pc[id];
      if (!x[id]) {
        continue;
      }
      a[r][c] = 0;
      int nr = r + dr[d[id]];
      int nc = c + dc[d[id]];
      pr[id] = nr;
      pc[id] = nc;
      if (!a[nr][nc]) {
        a[nr][nc] = id;
      } else {
        y[id] = true;
        ++u;
      }
    }

    if (u == N) {
      break;
    }
    ++t;
  }
  if (t <= 180) {
    cout << t << endl;
  } else {
    cout << "NA" << endl;
  }
}

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