#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <algorithm>
#include <set>
#include <map>
#include <bitset>
#include <cmath>
#include <functional>
#include <iomanip>
#define vll vector<ll>
#define vvvl vector<vvl>
#define vvl vector<vector<ll>>
#define VV(a, b, c, d) vector<vector<d>>(a, vector<d>(b, c))
#define VVV(a, b, c, d) vector<vvl>(a, vvl(b, vll (c, d)));
#define re(c, b) for(ll c=0;c<b;c++)
#define rep(a,b,c) for(ll a=b;a<c;a++)
#define all(obj) (obj).begin(), (obj).end()
typedef long long int ll;
typedef long double ld;
using namespace std;

void get(vll &a){re(i,a.size()) scanf("%lld",&a[i]);}
void get(vvl &a){re(i,a.size()) re(j,a[0].size()) scanf("%lld",&a[i][j]);}
void print(vll &a){re(i,a.size()) cout<<a[i]<<(i==a.size()-1?"\n":" ");}
void print(vvl &a){re(i,a.size()) re(j,a[0].size())cout<<a[i][j]<<(j==a[0].size()-1?"\n":" ");}


int main() {
  ll h, w;std::cin >> h >> w;
  vector<string> s(h);
  re(i, h) std::cin >> s[i];

  re(x, h){
    for(int y=-w+1;y<w;y++){
      if(x==0&&y==0) continue;
      bool f = true;
      ll cnt = 0;
      vector<string> t = s;

      if(y>=0){
        for(int i=0;i<h;i++){
          for(int j=0;j<w;j++){
            if(t[i][j]=='.') continue;
            t[i][j] = '.';
            if(i+x<h&&j+y>=0&&j+y<w&&t[i+x][j+y]=='#'){
              cnt++;
              t[i+x][j+y] = '.';
            }else{
              f = false;
            }
          }
        }
      }else{
        for(int i=0;i<h;i++){
          for(int j=w-1;j>=0;j--){
            if(t[i][j]=='.') continue;
            t[i][j] = '.';
            if(i+x<h&&j+y>=0&&j+y<w&&t[i+x][j+y]=='#'){
              cnt++;
              t[i+x][j+y] = '.';
            }else{
              f = false;
            }
          }
        }
      }
      if(f&&cnt){
        //std::cout << x << " " << y << '\n';
        std::cout << "YES" << '\n';
        return 0;
      }
    }
  }
  std::cout << "NO" << '\n';
}