#include<iostream>
#include<set>
#include<map>
using namespace std;

typedef pair<int,int> P;

string id = "ENWS";

int dir(char a){
  for(int i=0;i<4;i++)if(a==id[i])return i;
  return -1;
}

int main(){
  int h,w;
  string grid[30];
  bool use[30][30];
  int dx[] = {1,0,-1,0},dy[] = {0,-1,0,1};

  while(cin >> w >> h && (w||h)){
    for(int i=0;i<h;i++)cin >> grid[i];

    int ans = 0;
    while(ans<=180){
      set<P> s;
      int num = 0;
      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++){
	  int d = dir(grid[i][j]);
	  if(0<=d){
	    num++;
	    for(int k=-1;k<3;k++){
	      int dd = (d+k+4)%4;
	      int sy = i+dy[dd], sx = j+dx[dd];
	      if(sy<0 || sx<0 || h<=sy || w<=sx)continue;
	      if(grid[sy][sx] == '.' || grid[sy][sx] == 'X'){
		grid[i][j] = id[dd];
		s.insert(P(sy,sx));
		break;
	      }
	    }
	  }
	}
      }
      if(!num)break;

      for(int i=0;i<h;i++)
	for(int j=0;j<w;j++)use[i][j] = false;

      set<P>::iterator ite;
      for(ite=s.begin();ite!=s.end();ite++){
	int i=(*ite).first,j=(*ite).second;
	if(!use[i][j] && (grid[i][j] == '.' || grid[i][j] == 'X')){
	  for(int k=0;k<4;k++){
	    int sy = i+dy[k], sx = j+dx[k];
	    if(sy<0 || sx<0 || h<=sy || w<=sx || use[sy][sx])continue;
	    int d = dir(grid[sy][sx]);
	    if(d<0)continue;
	    int dd = (k+2)%4;
	    if(d==dd){
	      grid[sy][sx] = '.';
	      if(grid[i][j]!='X')grid[i][j] = id[d];
	      use[sy][sx] = true;
	      break;
	    }
	  }
	}
	use[i][j] = true;
      }
      ans++;
    }
    if(ans>180)cout << "NA\n";
    else cout << ans << endl;
  }
}