#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];
  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] = inv_dir(dd);
		s.insert(P(sy,sx));
		break;
	      }
	    }
	  }
	}
      }

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