function main(input){
    let lines = input.split("\n");
    let i = 0;
    while(lines[i]!=="0 0"){
        console.log(board(lines[i]));
        i++;
    }
    
    
}

function board(line){
    let args = line.split(" ").map(item=>parseInt(item));
    let height = args[0];
    let width = args[1];
    let put ="";
    let color = ["#","."];

    for(let i=0;i<height;i++){
        for(let j=0;j<width;j++){
            put+=color[(i+j)%2];
        }
        put+="\n";
    }
    return put;
    
    
    
    
    
}


main(require("fs").readFileSync("/dev/stdin","utf-8"));
