#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
using ll=long long;
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
template<class T> bool chmax(T &a, T b){if (a < b){a = b;return true;} else return false;}
template<class T> bool chmin(T &a, T b){if (a > b){a = b;return true;} else return false;}

struct UnionFind {
private:
    vector<int> par, siz;

public:
    UnionFind(int n) : par(n, -1), siz(n, 1) {}
    int find(int x) {
        if (par[x] == -1) return x;
        else {
            par[x] = find(par[x]);
            return par[x];
        }
    }
    bool same(int x, int y) {
        return find(x) == find(y);
    }
    int size(int x) {
        return siz[find(x)];
    }
    bool merge(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) return false;
        if (siz[x] < siz[y]) swap(x, y);
        siz[x] += siz[y];
        par[y] = x;
        return true;
    }
};

const int INF=1<<30;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int H,W;
    cin>>H>>W;
    vector<string>S(H);
    for(int i=0;i<H;i++)cin>>S[i];
    UnionFind uf1(H*W),uf2(H*W);
    for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            if(S[i][j]=='#'){
                if(i+1<H&&j+1<W&&S[i+1][j+1]=='#'){
                    uf1.merge(W*i+j,W*(i+1)+j+1);
                }
                if(i+1<H&&j-1>=0&&S[i+1][j-1]=='#'){
                    uf2.merge(W*i+j,W*(i+1)+j-1);
                }
            }
        }
    }
    vector<int>min1(H*W,INF),max1(H*W,-INF),min2(H*W,INF),max2(H*W,-INF);
    for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            chmin(min1[uf1.find(W*i+j)],i);
            chmax(max1[uf1.find(W*i+j)],i);
            chmin(min2[uf2.find(W*i+j)],i);
            chmax(max2[uf2.find(W*i+j)],i);
        }
    }
    vector flag1(H,vector<bool>(W));
    for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            if(flag1[i][j]||S[i][j]=='.')continue;
            int l1=uf1.find(W*i+j);
            if(min1[l1]==INF)continue;
            int l=INF,r=-INF;
            for(int k=min1[l1];k<=max1[l1];k++){
                flag1[k][j-i+k]=true;
                int l2=uf2.find(W*k+(j-i+k));
                if(min2[l2]==INF)continue;
                int a=min(k-min2[l2],max2[l2]-k);
                if(min2[l2]!=max2[l2]){
                    chmin(l,k-a);
                    chmax(r,k+a);
                }
            }
            if(!(l<=min1[l1]&&max1[l1]<=r)){
                cout<<"No"<<"\n";
                return 0;
            }
        }
    }
    vector flag2(H,vector<bool>(W));
    for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            if(flag2[i][j]||S[i][j]=='.')continue;
            int l2=uf2.find(W*i+j);
            if(min2[l2]==INF)continue;
            int l=INF,r=-INF;
            for(int k=min2[l2];k<=max2[l2];k++){
                flag2[k][j+i-k]=true;
                int l1=uf1.find(W*k+(j+i-k));
                if(min1[l1]==INF)continue;
                int a=min(k-min1[l1],max1[l1]-k);
                if(min1[l1]!=max1[l1]){
                    chmin(l,k-a);
                    chmax(r,k+a);
                }
            }
            if(!(l<=min2[l2]&&max2[l2]<=r)){
                cout<<"No"<<"\n";
                return 0;
            }
        }
    }
    cout<<"Yes"<<"\n";
}