var arr = [1,2]

function rectCover(number)
{
    if(number==0){
        return 0
    }
    if(number==1||number==2){
        return arr[number-1]
    }else{
        for(let i =2;i<number;i++){
            arr[i] = arr[i-2]+arr[i-1]
        }
        return arr[number-1]
    }
}