const main = input => input.split('\n').slice(1).filter(x => x)
    .map(line => line.split('').map(x => x === '#' ? 1 : 0))
    .find((vs, i, matrix) => vs
        .find((v, j) => v &&
            [[i - 1, j], [i + 1, j], [i, j - 1], [i, j + 1]]
                .map(t => (matrix[t[0]] && matrix[t[0]][t[1]]))
                .filter(x => x)
                .length === 0
        ) !== undefined
    ) ? 'No' : 'Yes';

console.log(main(require('fs').readFileSync('/dev/stdin', 'utf8')));
