Convert octal number to decimal number c program

#include <stdio.h>
#include <math.h>

int main()
{

    long int octal, decimal = 0;
    int i = 0;

    printf("Enter any octal number: ");
    scanf("%ld", &octal);
   
    while (octal != 0)
    {
        decimal = decimal + (octal % 10) * pow(8, i++);
        octal = octal / 10;
    }
    printf("Equivalent decimal value: %ld", decimal);
    return 0;
}

Output :

Enter any octal number: 67
Equivalent decimal value: 55