How to solve it by computer 2.9

#include <iostream>
using namespace std;

int main(int argc, char *argv[])
{
    int octal, digit;
    int decimal=0;
    int power= 1;
   
    cout<<"Inputan octal number: ";
    cin>>octal;
   
    for(int n=octal;n>0;n/=10)
    {
        digit = n%10;
        decimal=decimal+power*digit;
        power *=8;
    }
    cout<<"Octal("<<octal<<")Desimal("<<decimal<<")\n";
    return 0;
}