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

typedef pair<int,int> P;

int dir(char a){
  if(a=='E')return 0;
  if(a=='N')return 1;
  if(a=='W')return 2;
  if(a=='S')return 3;
  return -1;
}

char inv_dir(int a){
  if(a==0)return 'E';
  if(a==1)return 'N';
  if(a==2)return 'W';
  return 'S';
}

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){

      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] = inv_dir(dd);
		break;
	      }
	    }
	  }
	}
      }
      if(!num)break;
      for(int i=0;i<h;i++)
	for(int j=0;j<w;j++)use[i][j] = false;

      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++){
	  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] = inv_dir(d);
		use[i][j] = true;
		use[sy][sx] = true;
		break;
	      }
	    }
	  }
	}
      }
      ans++;
      /*
      if(ans<10){
	cout << ans << endl;
	for(int i=0;i<h;i++)cout << grid[i] << endl;
	cout << endl;
      }
      */
    }
    if(ans>180)cout << "NA\n";
    else cout << ans << endl;
  }
}