Strange counter

Problem link:https://www.hackerrank.com/challenges/strange-code/problem

#include <bits/stdc++.h>
using namespace std;
int main()
{
    double a,b,c,d;
    long long int t,k;
    cin>>t;
    a=log((t+3)/3);
    b=log(2);
    k=a/b;
    c=3*pow(2,k-1+1);
    d=t-(3*(pow(2,k)-1))-1;
    if((3*pow(2,k)-1)!=t)
    {
        cout<<c-d;
    }
    else
    {
        cout<<"1";
    }
    //cout<<c<<" "<<d<<" "<<k;
}

The above code is not working for t=1000000000000