#include <iostream>
#include <string>
#include <cstdio>
#include <vector>

typedef long long ll;
using namespace std;
#define rep(i,b) for(ll i=0;i<(b);++i)
#define rep1(i,b) for(ll i=1;i<=(b);++i)
#define vec vector
#define FOR(I,A,B) for(ll I=(A);I<(B);++I)
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << endl;

// http://procon-nenuon61.hatenablog.com/entry/2017/03/11/143154

int main() {
   int H, W;
   cin >> H >> W;
   vector<string> mass(H);
   rep(i, H) cin >> mass[i];

   bool isPainted[H][W];
   rep(i, H) rep(j, W) isPainted[i][j] = false;

   bool check = false;
   FOR(dy, -H, H) {
      FOR(dx, -W, W) {
         if (dy == 0 && dx == 0) continue;

         rep(i, H) rep(j, W) isPainted[i][j] = false;

         rep(z, (H-1)*W+W) {
            int y = z/W;
            int x = z%W;
            if (mass[y][x] == '#' && isPainted[y][x] == false) {
               isPainted[y][x] = true;
               if (y+dy<0 || y+dy>=H || x+dx<0 || x+dx>=W) {
                  check = false; break;
               }
               if (mass[y+dy][x+dx]=='#' && isPainted[y+dy][x+dx] == false) {
                  isPainted[y+dy][x+dx] = true;
                  check = true;
               } else {
                  check = false;
                  break;
               }
            }
         }

         if (check) {
            cout << "YES" << endl;
            return 0;
         }
      }
   }
   cout << "NO" << endl;
}