#include<bits/stdc++.h>
using namespace std;
using ll = long long;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl
#define p_yes() p("YES")
#define p_no() p("NO")

ll H, W;    

bool check(vector<string> S, ll dx, ll dy){
    ll paint_count = 0;
    FOR(y, 0, H){
        FOR(x, 0, W){
            if(S[y][x]=='#'){
                S[y][x] = 'R';
                paint_count++;

                // その平行移動先は青く塗る
                ll tx = x + dx;
                ll ty = y + dy;
                if(0<=tx && tx<W && 0<=ty && ty<H){
                    if(S[ty][tx]=='#'){
                        S[ty][tx] = 'B';
                    }else{
                        return false;
                    }
                }else{
                    return false;
                }
            }
        }
    }

    if(paint_count){
        return true;
    }else{
        return false;
    }
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    cin >> H >> W;

    vector<string> S(H);
    FOR(i, 0, H){
        cin >> S[i];
    }

    // x方向移動量0の場合
    FOR(dx, 1, W){ // 平行移動量
        ll dy = 0;
        if(check(S, dx, dy)){
            p_yes();
            return 0;
        }
    }

    FOR(dx, -W, W){
        FOR(dy, 1, H){
            if(check(S, dx, dy)){
                p_yes();
                return 0;
            }   
        }
    }

    p_no();

    return 0;
}