Odd Results From Octal-decimal Converter

I wrote this small program to take an octal number from the user and convert it to decimal form.

import java.util.Scanner;
public class Decimal
{
public static void main (String args []) //gets octal number from user, later prints conversion
{
int octal;

[Code] .....

Some conversions work. For example, 77 will be correctly converted to 63, and 77777777 will be converted to 16777215. However, some conversions do not work. An example of this is 775002 gets converted to 74898.