#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)

using namespace std;

string s[30];
int h,w;
int dx[4] = {1,0,-1,0},dy[4] = {0,1,0,-1};

pair<int,int> NextPoint(int y,int x)
{
	pair<int,int> p;
	if(s[y][x] == 'E')
	{
		if(s[y+1][x] == '.' || s[y+1][x] == 'X')
		{
			s[y][x] = 'S';

			p.first = y+1;
			p.second = x;
			return p;
		}
		else if(s[y][x+1] == '.' || s[y][x+1] == 'X')
		{
			s[y][x] = 'E';

			p.first = y;
			p.second = x+1;
			return p;
		}
		else if(s[y-1][x] == '.' || s[y-1][x] == 'X')
		{
			s[y][x] = 'N';

			p.first = y-1;
			p.second = x;
			return p;
		}
		else if(s[y][x-1] == '.' || s[y][x-1] == 'X')
		{
			s[y][x] = 'W';

			p.first = y;
			p.second = x-1;
			return p;
		}
	}
	else if(s[y][x] == 'N')
	{
		if(s[y][x+1] == '.' || s[y][x+1] == 'X')
		{
			s[y][x] = 'E';

			p.first = y;
			p.second = x+1;
			return p;
		}
		else if(s[y-1][x] == '.' || s[y-1][x] == 'X')
		{
			s[y][x] = 'N';

			p.first = y-1;
			p.second = x;
			return p;
		}
		else if(s[y][x-1] == '.' || s[y][x-1] == 'X')
		{
			s[y][x] = 'W';

			p.first = y;
			p.second = x-1;
			return p;
		}
		else if(s[y+1][x] == '.' || s[y+1][x] == 'X')
		{
			s[y][x] = 'S';

			p.first = y+1;
			p.second = x;
			return p;
		}
	}
	else if(s[y][x] == 'W')
	{
		if(s[y-1][x] == '.' || s[y-1][x] == 'X')
		{
			s[y][x] = 'N';

			p.first = y-1;
			p.second = x;
			return p;
		}
		else if(s[y][x-1] == '.' || s[y][x-1] == 'X')
		{
			s[y][x] = 'W';

			p.first = y;
			p.second = x-1;
			return p;
		}
		else if(s[y+1][x] == '.' || s[y+1][x] == 'X')
		{
			s[y][x] = 'S';

			p.first = y+1;
			p.second = x;
			return p;
		}
		else if(s[y][x+1] == '.' || s[y][x+1] == 'X')
		{
			s[y][x] = 'E';

			p.first = y;
			p.second = x+1;
			return p;
		}
	}
	else if(s[y][x] == 'S')
	{
		if(s[y][x-1] == '.' || s[y][x-1] == 'X')
		{
			s[y][x] = 'W';

			p.first = y;
			p.second = x-1;
			return p;
		}
		else if(s[y+1][x] == '.' || s[y+1][x] == 'X')
		{
			s[y][x] = 'S';

			p.first = y+1;
			p.second = x;
			return p;
		}
		else if(s[y][x+1] == '.' || s[y][x+1] == 'X')
		{
			s[y][x] = 'E';
			p.first = y;
			p.second = x+1;
			return p;
		}
		else if(s[y-1][x] == '.' || s[y-1][x] == 'X')
		{
			s[y][x] = 'N';

			p.first = y-1;
			p.second = x;
			return p;
		}
	}
}

bool can(int y,int x)
{
	if(0 <= y & y < h && 0 <= x && x < w)
	{
		return true;
	}
	else return false;
}

bool isPerson(int y,int x)
{
	if(s[y][x] == 'E' || s[y][x] == 'W' || s[y][x] == 'S' || s[y][x] == 'N')
	{
		return true;
	}
	else return false;
}

int main()
{

	while(cin >> w >> h)
	{
		if(w == 0 && h == 0) break;

		rep(i,h)
		{
			cin >> s[i];
		}

		bool flag = true;
		rep(i,h)
		{
			rep(j,w)
			{
				if(s[i][j] == 'E' || s[i][j] == 'W' || s[i][j] == 'S' || s[i][j] ==  'N')
				{
					flag = false;
				}
			}
		}

		if(flag)
		{
			cout << 0 << endl;
			return 0;
		}



		rep(k,180)
		{
			vector<pair<int,int> > v;
			rep(i,h) 
			{
				rep(j,w) 
				{	
					if(isPerson(i,j)) v.push_back(NextPoint(i,j));
				}
			}


			bool used[30][30];
			rep(i,h) rep(j,w) used[i][j] = true;

			
			
			rep(i,v.size())
			{
				int y = v[i].first;
				int x = v[i].second;

				if(can(y,x+1) && isPerson(y,x+1) && used[y][x+1] && used[y][x])
				{
					if(s[y][x] == 'X')
					{
						s[y][x+1] = '.';
					}
					else
					{
						s[y][x] = s[y][x+1];
						s[y][x+1] = '.';
					}
					used[y][x+1] = false;
					used[y][x] = false;
				}
				else if(can(y-1,x) && isPerson(y-1,x) && used[y-1][x] && used[y][x])
				{
					if(s[y][x] == 'X')
					{
						s[y-1][x] = '.';
					}
					else
					{
						swap(s[y][x],s[y-1][x]);
					}
					used[y-1][x] = false;
					used[y][x] = false;
				}
				else if(can(y,x-1) && isPerson(y,x-1) && used[y][x-1] && used[y][x])
				{
					if(s[y][x] == 'X')
					{
						s[y][x-1] = '.';
					}
					else
					{
						s[y][x] = s[y][x-1];
						s[y][x-1] = '.';
					}
					used[y][x-1] = false;
					used[y][x] = false;
				}
				else if(can(y+1,x) && isPerson(y+1,x) && used[y+1][x] && used[y][x])
				{
					if(s[y][x] == 'X')
					{
						s[y+1][x] = '.';
					}
					else
					{
						s[y][x] = s[y+1][x];
						s[y+1][x] = '.';
					}
					used[y+1][x] = false;
					used[y][x] = false;
				}
			}


			bool flag_2 = true;
			rep(i,h)
			{
				rep(j,w)
				{
					if(s[i][j] == 'E' || s[i][j] == 'N' || s[i][j] == 'W' || s[i][j] == 'S')
					{
						flag_2 = false;
					}
				}
			}

			if(flag_2)
			{
				cout << k+1 << endl;
				flag = true;
				break;
			}

		}

		if(!flag) cout << "NA" << endl;

	}
	return 0;
}