#include <bits/stdc++.h>
 
using namespace std;
 
#define MAX 35
typedef vector<char> Vec;
typedef vector<Vec> Mat;
 
struct Person {
    int x, y, d;
    Person(){}
    Person(int x, int y, int d)
        : x(x), y(y), d(d) {}
};
 
int W, H;
vector<Person> v;
const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, -1, 0, 1};
 
bool inField(int x, int y)
{
    return (0 <= x && x < W && 0 <= y && y < H);
}
 
int getD(int d, int x)
{
    int v[] = {1, 0, 3, 2};
    return (v[(x-d+4)%4]);
}
 
void solve(Mat &maze)
{
    for (int T = 0; T < 180; T++) {
        int N = v.size();
        vector<Person> v2(N), v3 = v;
        int cnt[MAX][MAX] = {{}}, num[MAX][MAX];
        memset(num, -1, sizeof(num));
 
        for (int i = 0; i < N; i++) {
            int d = (4 - v[i].d) % 4;
            for (int j = 0; j < 4; j++) {
                int nd = (d + j) % 4;
                int nx = v[i].x + dx[nd];
                int ny = v[i].y + dy[nd];
                if (maze[ny][nx] == '.' || maze[ny][nx] == 'X') {
                    cnt[ny][nx]++;
                    num[v[i].y][v[i].x] = i;
                    v2[i] = Person(nx,ny,getD(v[i].d,j));
                    v3[i].d = getD(v[i].d,j);
                    break;
                }
            }
        }
        v.clear();
        bool used[MAX*MAX] = {0};
        const int dx2[] = {1, 0, -1, 0};
        const int dy2[] = {0, -1, 0, 1};
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                if (cnt[i][j] == 0) continue;
                for (int k = 0; k < 4; k++) {
                    int nx = j + dx2[k];
                    int ny = i + dy2[k];
                    int idx = num[ny][nx];
                    if (!inField(nx, ny)) continue;
                    if (i != v2[idx].y ||
                       j != v2[idx].x) continue;
                     
                    if (idx != -1) {
                        maze[ny][nx] = '.';
                        if (maze[i][j] == '.') {
                            maze[i][j] = '*';
                            v.push_back(v2[idx]);
                        }
                        used[idx] = 1;
                        break;
                    }
                }
            }
        }
        for (int i = 0; i < N; i++) {
            if (!used[i]) {
                v.push_back(v3[i]);
            }
        }
        if (v.size() == 0) {
            cout << T+1 << endl;
            return;
        }
    }
    cout << "NA" << endl;
}
 
int main()
{
    while (cin >> W >> H, W) {
        Mat maze(H, Vec(W));
        v.clear();
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                cin >> maze[i][j];
                if (maze[i][j] == 'N') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 0));
                } else if (maze[i][j] == 'E') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 1));
                } else if (maze[i][j] == 'S') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 2));
                } else if (maze[i][j] == 'W') {
                    maze[i][j] = '*';
                    v.push_back(Person(j, i, 3));
                }
            }
        }
        solve(maze);
    }
    return 0;
}

Measured memory_bytes: 3076