#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>

using namespace std;

#ifdef _MSC_VER
#define __typeof__ decltype

template <class T>
int __builtin_popcount(T n) { return n ? 1 + __builtin_popcount(n & (n - 1)) : 0; }
#endif

#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
#define all(c) (c).begin(), (c).end()
#define rall(c) (c).rbegin(), (c).rend()
#define popcount __builtin_popcount

const double EPS = 1e-8;
typedef long long ll;
typedef pair<int, int> pint;


int main()
{
	int W, H;
	int dx[] = { 1, 0, -1, 0 };
	int dy[] = { 0, -1, 0, 1 };
	char* dirs = "ENWS";

	while (scanf("%d%d", &W, &H), W | H)
	{
		char maze[64][64];
		for (int i = 0; i < H; ++i)
			scanf("%s", maze + i);

		int time;
		for (time = 1; time <= 180; ++time)
		{
			int left = 0;
			bool canMove[64][64];
			bool dest[64][64];
			memset(canMove, 0, sizeof(canMove));
			memset(dest, 0, sizeof(dest));
			for (int i = 0; i < H; ++i)
			{
				for (int j = 0; j < W; ++j)
				{
					char* hoge = strchr(dirs, maze[i][j]);
					if (!hoge)
						continue;

					++left;

					int dir = hoge - dirs;
					int next_dir = -1;
					for (int k = -1; k < 3; ++k)
					{
						int d = (dir + k + 4) % 4;
						int tx = j + dx[d];
						int ty = i + dy[d];
						if (tx < 0 || ty < 0 || tx >= W || ty >= H)
							continue;

						char c = maze[ty][tx];
						if (c == '.' || c == 'X')
						{
							next_dir = d;
							break;
						}
					}
					if (next_dir != -1)
					{
						maze[i][j] = dirs[next_dir];
						dest[i+dy[next_dir]][j+dx[next_dir]] = true;
						canMove[i][j] = true;
					}
				}
			}

			for (int i = 0; i < H; ++i)
			{
				for (int j = 0; j < W; ++j)
				{
					if (!dest[i][j])
						continue;

					int k;
					int tx, ty;
					for (k = 0; k < 4; ++k)
					{
						tx = j + dx[k];
						ty = i + dy[k];
						char* pp;
						if (tx >= 0 && ty >= 0 && tx < W && ty < H
							&& (pp = strchr(dirs, maze[i+dy[k]][j+dx[k]])) != NULL
							&& pp - dirs < 4 && maze[ty][tx] == dirs[(k+2)%4]
						&& canMove[ty][tx])
						{
							if (maze[i][j] == '.')
								maze[i][j] = maze[ty][tx];
							else
								--left;
							break;
						}
					}
					maze[ty][tx] = '.';
				}
			}

			if (!left)
				break;
		}
		if (time != 181)
			printf("%d\n", time);
		else
			puts("NA");
	}

	return 0;
}