#include <bits/stdc++.h>
using namespace std;
#define all(c) (c).begin(),(c).end()
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;i--)
#define REP(i,m,n) for(int i=(int)(m);i<(int)(n);i++)
#define rep(i,n) REP(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
#define pb(a) push_back(a)
#define pr(a) cout<<(a)<<endl
#define PR(a,b) cout<<(a)<<" "<<(b)<<endl
#define R cin>>
#define F first
#define S second
#define ll long long
bool check(int n,int m,int x,int y){return x>=0&&x<n&&y>=0&&y<m;}
const ll MAX=1000000007,MAXL=1LL<<60,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
typedef pair<int,int> P;

int main() {
  int n,m;
  cin >> n >> m;
  string s[n];
  rep(i,n) cin >> s[i];
  bool ck=false;
  rep(p,n) {
    rep(q,m) {
      if(!p&&!q) continue;
      bool u[n][m];
      memset(u,0,sizeof(u));
      bool ck2=true;
      bool ck3=false;
      rep(i,n) {
	rep(j,m) {
	  if(s[i][j]!='#' || u[i][j]) continue;
	  if(!check(n,m,i+p,j+q) || s[i+p][j+q]!='#' || u[i+p][j+q]) {
	    ck2=false;
	    break;
	  }
	  u[i][j]=1;
	  u[i+p][j+q]=1;
	  ck3=1;
	}
      }
      if(ck2 && ck3) ck=1;
    }
  }
  if(ck) cout << "YES" << endl;
  else cout << "NO" << endl;
  return 0;
}