def main():
    H, W = map(int, input().split())
    S = []
    for _ in range(H):
        S.append(input())

    # #の累積を取る
    i_j1 = {}
    i_j2 = {}
    for i in range(H):
        for j in range(W):
            x = i + j
            y = i - j
            if x not in i_j1:
                i_j1[x] = []
            i_j1[x].append(i)
            if y not in i_j2:
                i_j2[y] = []
            i_j2[y].append(i)
    
    i_j1_cums = {}
    for key, values in i_j1.items():

        values.sort()
        new_values = []
        c = 0
        for i in values:
            j = key - i
            if S[i][j] == "#":
                c += 1
            new_values.append(c)
        
        value_map = {}
        for i in range(len(values)):
            v = new_values[i]
            k = values[i]
            value_map[k] = v
        i_j1_cums[key] = value_map
        
    i_j2_cums = {}
    for key, values in i_j2.items():
        values.sort()
        new_values = []
        c = 0
        for i in values:
            j = i - key
            if S[i][j] == "#":
                c += 1
            new_values.append(c)
        
        value_map = {}
        for i in range(len(values)):
            v = new_values[i]
            k = values[i]
            value_map[k] = v
        i_j2_cums[key] = value_map

    i_j1_imos= {}
    i_j2_imos= {}    
    for i in range(H):
        for j in range(W):
            if S[i][j] == "#":
                is_ok = True
                for di, dj in ((1, 1), (1, -1), (-1, 1), (- 1, -1)):
                    new_i = di + i
                    new_j = dj + j
                    if not (0 <= new_i < H and 0 <= new_j < W):
                        is_ok = False
                        break
                    if S[new_i][new_j] == ".":
                        is_ok = False
                        break

                if not is_ok:
                    continue

                # i_j1
                def solve(ar, i, mid):
                    high_i = i + mid
                    low_i = i - mid

                    if high_i not in ar:
                        return False
                    
                    if low_i not in ar:
                        return False
                    
                    if (low_i - 1) not in ar:
                        x = ar[high_i]
                        return x == 1 + 2 * mid
                    else:
                        x = ar[high_i]
                        x1 = ar[low_i - 1]
                        return (x - x1) == 1 + 2 * mid

                key = i + j
                ar = i_j1_cums[key]
                low = 1
                high = max(H, W)
                while high - low > 1:
                    mid = (high + low) // 2

                    if solve(ar, i, mid):
                        low = mid
                    else:
                        high = mid
                if solve(ar, i, high):
                    ij1_val = high
                else:
                    ij1_val = low

                
                key = i - j
                ar = i_j2_cums[key]
                low = 1
                high = max(H, W)
                while high - low > 1:
                    mid = (high + low) // 2

                    if solve(ar, i, mid):
                        low = mid
                    else:
                        high = mid
                if solve(ar, i, high):
                    ij2_val = high
                else:
                    ij2_val = low
                ans = min(ij1_val, ij2_val)

                key = i + j
                if key not in i_j1_imos:
                    i_j1_imos[key] = {}
                min_i = i - ans
                max_i = i + ans + 1
                if min_i not in i_j1_imos[key]:
                    i_j1_imos[key][min_i] = 0
                i_j1_imos[key][min_i] += 1
                if max_i not in i_j1_imos[key]:
                    i_j1_imos[key][max_i] = 0
                i_j1_imos[key][max_i] -= 1

                key = i - j
                if key not in i_j2_imos:
                    i_j2_imos[key] = {}
                min_i = i - ans
                max_i = i + ans + 1
                if min_i not in i_j2_imos[key]:
                    i_j2_imos[key][min_i] = 0
                i_j2_imos[key][min_i] += 1
                if max_i not in i_j2_imos[key]:
                    i_j2_imos[key][max_i] = 0
                i_j2_imos[key][max_i] -= 1
    
    passed = [[0] * W for _ in range(H)]
    for key, values_map in i_j1_imos.items():
        min_i = min(values_map.keys())
        max_i = max(values_map.keys())

        c = 0
        for i in range(max_i - min_i):
            i0 = min_i + i
            if i0 in values_map:
                c += values_map[i0]
            
            j0 = key - i0
            passed[i0][j0] += c

    for key, values_map in i_j2_imos.items():
        min_i = min(values_map.keys())
        max_i = max(values_map.keys())

        c = 0
        for i in range(max_i - min_i):
            i0 = min_i + i
            if i0 in values_map:
                c += values_map[i0]
            
            j0 = i0 - key
            passed[i0][j0] += c

    is_ok = True
    for i in range(H):
        for j in range(W):
            if passed[i][j] > 0 and S[i][j] == ".":
                is_ok = False
            elif passed[i][j] == 0 and S[i][j] == "#":
                is_ok = False
    if is_ok:
        print("Yes")
    else:
        print("No")
            











if __name__ == "__main__":
    main()