kek

if (len == 0){
        for (int i =0; i<nums.size();++i){
            cout<<nums[i];
        }
        cout<<endl;
        return;
    }
    if (ones == len ){
        nums.push_back(1);
        fuck(len - 1, ones-1);
        nums.pop_back();
        return;
    }
    nums.push_back(0);
    fuck(len-1,ones);
    nums.pop_back();
    if (ones>0){
        nums.push_back(1);
        fuck(len-1,ones-1);
        nums.pop_back();
    }
    return;