concatenate binary of first N integers and return decimal value

Question

Example,

N = 3 The first N integers for value 3 is 1, 2, 3

Binary

Answer 1

    cin>>n;
    ll ans=1;
    ll one=1;
    for(int i=2;i<=n;i++)
    {
        ll digit=log2(i)+1;
        ans=(((ans%N*(one<