Count total set bits

//User function Template for C++

// Function to count set bits in the given number x
// n: input to count the number of set bits

int countSetBits(int n){
    // Ignore 0 as all the bits are unset 
    n++; 
  
    // To store the powers of 2 
    int powerOf2 = 2; 
  
    // To store the result, it is initialized 
    // with n/2 because the count of set 
    // least significant bits in the integers 
    // from 1 to n is n/2 
    int cnt = n / 2; 
  
    // Loop for every bit required to represent n 
    while (powerOf2 <= n) { 
  
        // Total count of pairs of 0s and 1s 
        int totalPairs = n / powerOf2; 
  
        // totalPairs/2 gives the complete 
        // count of the pairs of 1s 
        // Multiplying it with the current power 
        // of 2 will give the count of 
        // 1s in the current bit 
        cnt += (totalPairs / 2) * powerOf2; 
  
        // If the count of pairs was odd then 
        // add the remaining 1s which could 
        // not be groupped together 
        cnt += (totalPairs & 1) ? (n % powerOf2) : 0; 
  
        // Next power of 2 
        powerOf2 <<= 1; 
    } 
  
    // Return the result 
    return cnt; 
}