#include<iostream>
using namespace std;
char map[55][55];
int main(){
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++)scanf("%s",map[i]+1);
    int flag=1;
    cnt=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(map[i][j]=='#'){
                cnt++;
                if(map[i-1][j]=='#'||map[i][j-1]=='#'||map[i][j-1]=='#'||map[i][j-1]=='#')flag=1;
                else flag=0;
            }
        }
    }
    if(flag||cnt==1)cout<<"Yes";
    else cout<<"No";
    return 0;    
}
