function main(lines) {
    const input = lines.split('\n')

        let result = ''
    for(let i=0; i<input.length; i++){
        const arrayNum = input[i].split(' ').map(Number)
        const H = arrayNum[0]
        const W = arrayNum[1]
        const odd = Array(W+1).join('#.').slice(0,W) + '\n'
        const even = Array(W+1).join('.#').slice(0,W) + '\n'

        for(let i=1; i<H+1; i++){
            result += (i%2 === 0 ? even : odd)
        }

        if(H === 0 && W === 0) break;
        result += '\n'
    }
    console.log(result.trim() + '\n')
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));

