#include<bits/stdc++.h>
using lint=long long;
int main(){
    std::cin.tie(nullptr);std::ios_base::sync_with_stdio(false);
    std::cout.setf(std::ios_base::fixed);std::cout.precision(15);
    lint h,w;std::cin>>h>>w;
    std::vector<std::vector<lint>>a(h,std::vector<lint>(w));
    bool found=false;
    for(lint i=0;i<h;i++){
        for(lint j=0;j<w;j++){
            char c;std::cin>>c;
            a.at(i).at(j)=c=='#';
            found|=a.at(i).at(j);
        }
    }
    if(!found){
        std::cout<<"NO"<<'\n';
        return 0;
    }
    for(lint q=0;q<2;q++){
        for(lint di=0;di<h;di++){
            for(lint dj=0;dj<w;dj++){
                if(!di&&!dj)continue;
                auto b=a;
                for(lint i=0;i<h;i++){
                    for(lint j=0;j<w;j++){
                        if(!b.at(i).at(j))continue;
                        lint ni=i+di,nj=j+dj;
                        if(h<=ni||w<=nj||!std::exchange(b.at(ni).at(nj),false)){
                            goto Impossible;
                        }
                    }
                }
                std::cout<<"YES"<<'\n';
                return 0;
    Impossible:;
            }
        }
        for(auto&&b:a)std::reverse(b.begin(),b.end());
    }
    std::cout<<"NO"<<'\n';
}