Count Total Setbits.cpp

class Solution {
  public:
    long long solve( long long n){
        if(n==0)
        return 0;
        
        long long ans=0, x=(long long)log2(n);
        long long upto2= x*(pow(2,x-1));
        long long msb= n-pow(2,x)+1;
        
        long long rest= n-pow(2,x);
        
        ans+= upto2+ msb + solve(rest);
        
        return ans;
    }
 
    long long countBits(long long N) {
        return solve(N);
    }
};