Binary to Octal

#include <iostream>
#include <cmath>

using namespace std;
int convertBinarytoOctal(long long);
int convertBinarytoOctal(long long binaryNumber) {
  int octalNumber = 0, decimalNumber = 0, i = 0;
  while(binaryNumber != 0){
    decimalNumber += (binaryNumber%10) * pow(2,i);
    ++i;
    binaryNumber/=10;
  }
  i = 1;
  while (decimalNumber != 0){
    octalNumber += (decimalNumber % 8) * i;
    decimalNumber /= 8;
    i *= 10;
  }
  return octalNumber;
}