#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int H,W;
    cin>>H>>W;
    vector<string> dat(H);
    FOR(i,H) cin>>dat[i];
    int blackNum = 0;
    FOR(i,H) FOR(j,W){
        if(dat[i][j] == '#') blackNum++;
    }
    FOR(dr,H) FOR(dc,W){
        int rem = blackNum;
        vector<string> tmp(dat);
        FOR(i,H) FOR(j,W){
            if(tmp[i][j] == '#'){
                if(i + dr < H && j + dc < W && tmp[i+dr][j+dc] == '#'){
                    tmp[i][j] = '.';
                    tmp[i+dr][j+dc] = '.';
                    rem -= 2;
                }
            }
        }
        if(rem == 0){
            //cout<<" "<<dr<<" "<<dc<<endl;
            puts("YES");
            return 0;
        }
    }
    cout<<"NO"<<endl;
    return 0;
}